Fix gpexpand flaky test cases

Each gpexpand test case need a new environment.
Previous code uses pkill to make sure no postgres
process remaining and then uses gpstop to double
confirm.

However, pkill to terminate cluster may over-kill
some other postgres process on the hosts. What's
more, the interface `Given a working directory of
the test as '/data/gpdata/gpexpand'` will remove
the directory which also remove the $MASTER_DATA_DIRECTORY,
so the following `gpstop` is useless because
$MASTER_DATA_DIRECTORY is gone. Also, this introduce
race conditon.

This commit removes pkill and use gpstop interface
to build a clean environment for each test case. Also
it makes sure that `gpstop` is invoked at the very
beginning of each test case.

gpMgmt/test/behave/mgmt_utils/gpexpand.feature

@@ -4,10 +4,9 @@ Feature: expand the cluster by adding more segments
     @gpexpand_no_mirrors
     @gpexpand_timing
     Scenario: after resuming a duration interrupted redistribution, tables are restored
-        Given a working directory of the test as '/data/gpdata/gpexpand'
-        And the database is killed on hosts "mdw,sdw1"
+	Given the database is not running
+	And a working directory of the test as '/data/gpdata/gpexpand'
         And a temporary directory under "/data/gpdata/gpexpand/expandedData" to expand into
-        And the database is not running
         And a cluster is created with no mirrors on "mdw" and "sdw1"
         And the master pid has been saved
         And database "gptest" exists
@@ -29,10 +28,9 @@ Feature: expand the cluster by adding more segments
     @gpexpand_timing
     @gpexpand_standby
     Scenario: after a duration interrupted redistribution, state file on standby matches master
-        Given a working directory of the test as '/data/gpdata/gpexpand'
-        And the database is killed on hosts "mdw,sdw1"
+    	Given the database is not running
+        And a working directory of the test as '/data/gpdata/gpexpand'
         And a temporary directory under "/data/gpdata/gpexpand/expandedData" to expand into
-        And the database is not running
         And a cluster is created with no mirrors on "mdw" and "sdw1"
         And the user runs gpinitstandby with options " "
         And database "gptest" exists
@@ -48,10 +46,9 @@ Feature: expand the cluster by adding more segments
     @gpexpand_no_mirrors
     @gpexpand_timing
     Scenario: after resuming an end time interrupted redistribution, tables are restored
-        Given a working directory of the test as '/data/gpdata/gpexpand'
-        And the database is killed on hosts "mdw,sdw1"
+        Given the database is not running
+        And a working directory of the test as '/data/gpdata/gpexpand'
         And a temporary directory under "/data/gpdata/gpexpand/expandedData" to expand into
-        And the database is not running
         And a cluster is created with no mirrors on "mdw" and "sdw1"
         And database "gptest" exists
         And there are no gpexpand_inputfiles
@@ -70,10 +67,9 @@ Feature: expand the cluster by adding more segments
     @gpexpand_no_mirrors
     @gpexpand_segment
     Scenario: expand a cluster that has no mirrors
-        Given a working directory of the test as '/data/gpdata/gpexpand'
-        And the database is killed on hosts "mdw,sdw1"
+        Given the database is not running
+        And a working directory of the test as '/data/gpdata/gpexpand'
         And a temporary directory under "/data/gpdata/gpexpand/expandedData" to expand into
-        And the database is not running
         And a cluster is created with no mirrors on "mdw" and "sdw1"
         And database "gptest" exists
         And there are no gpexpand_inputfiles
@@ -86,10 +82,9 @@ Feature: expand the cluster by adding more segments
     @gpexpand_no_mirrors
     @gpexpand_host
     Scenario: expand a cluster that has no mirrors with one new hosts
-        Given a working directory of the test as '/data/gpdata/gpexpand'
-        And the database is killed on hosts "mdw,sdw1,sdw2"
+        Given the database is not running
+        And a working directory of the test as '/data/gpdata/gpexpand'
         And a temporary directory under "/data/gpdata/gpexpand/expandedData" to expand into
-        And the database is not running
         And a cluster is created with no mirrors on "mdw" and "sdw1"
         And database "gptest" exists
         And there are no gpexpand_inputfiles
@@ -103,10 +98,9 @@ Feature: expand the cluster by adding more segments
     @gpexpand_no_mirrors
     @gpexpand_host_and_segment
     Scenario: expand a cluster that has no mirrors with one new hosts
-        Given a working directory of the test as '/data/gpdata/gpexpand'
-        And the database is killed on hosts "mdw,sdw1,sdw2"
+        Given the database is not running
+        And a working directory of the test as '/data/gpdata/gpexpand'
         And a temporary directory under "/data/gpdata/gpexpand/expandedData" to expand into
-        And the database is not running
         And a cluster is created with no mirrors on "mdw" and "sdw1"
         And database "gptest" exists
         And there are no gpexpand_inputfiles
@@ -120,10 +114,9 @@ Feature: expand the cluster by adding more segments
     @gpexpand_mirrors
     @gpexpand_segment
     Scenario: expand a cluster that has mirrors
-        Given a working directory of the test as '/data/gpdata/gpexpand'
-        And the database is killed on hosts "mdw,sdw1"
+        Given the database is not running
+        And a working directory of the test as '/data/gpdata/gpexpand'
         And a temporary directory under "/data/gpdata/gpexpand/expandedData" to expand into
-        And the database is not running
         And a cluster is created with mirrors on "mdw" and "sdw1"
         And database "gptest" exists
         And there are no gpexpand_inputfiles
@@ -135,10 +128,9 @@ Feature: expand the cluster by adding more segments
     @gpexpand_mirrors
     @gpexpand_host
     Scenario: expand a cluster that has mirrors with one new hosts
-        Given a working directory of the test as '/data/gpdata/gpexpand'
-        And the database is killed on hosts "mdw,sdw1,sdw2,sdw3"
+        Given the database is not running
+        And a working directory of the test as '/data/gpdata/gpexpand'
         And a temporary directory under "/data/gpdata/gpexpand/expandedData" to expand into
-        And the database is not running
         And a cluster is created with mirrors on "mdw" and "sdw1"
         And database "gptest" exists
         And there are no gpexpand_inputfiles
@@ -153,10 +145,9 @@ Feature: expand the cluster by adding more segments
     @gpexpand_host_and_segment
     @gpexpand_standby
     Scenario: expand a cluster that has mirrors with one new host
-        Given a working directory of the test as '/data/gpdata/gpexpand'
-        And the database is killed on hosts "mdw,sdw1,sdw2,sdw3"
+        Given the database is not running
+        And a working directory of the test as '/data/gpdata/gpexpand'
         And a temporary directory under "/data/gpdata/gpexpand/expandedData" to expand into
-        And the database is not running
         And a cluster is created with mirrors on "mdw" and "sdw1"
         And the user runs gpinitstandby with options " "
         And database "gptest" exists
@@ -170,10 +161,9 @@ Feature: expand the cluster by adding more segments
 
     @gpexpand_verify_redistribution
     Scenario: Verify data is correctly redistributed after expansion
-        Given a working directory of the test as '/data/gpdata/gpexpand'
-        And the database is killed on hosts "localhost"
+        Given the database is not running
+        And a working directory of the test as '/data/gpdata/gpexpand'
         And a temporary directory under "/data/gpdata/gpexpand/expandedData" to expand into
-        And the database is not running
         And the cluster is generated with "1" primaries only
         And database "gptest" exists
         And the user connects to "gptest" with named connection "default"
@@ -192,11 +182,10 @@ Feature: expand the cluster by adding more segments
         Then distribution information from table "public.redistribute" with data in "gptest" is verified against saved data
 
     @gpexpand_verify_writable_external_redistribution
-    Scenario: Verify policy of writable external table is correctly updated after redistribution 
-        Given a working directory of the test as '/data/gpdata/gpexpand'
-        And the database is killed on hosts "localhost"
+    Scenario: Verify policy of writable external table is correctly updated after redistribution
+        Given the database is not running
+        And a working directory of the test as '/data/gpdata/gpexpand'
         And a temporary directory under "/data/gpdata/gpexpand/expandedData" to expand into
-        And the database is not running
         And the cluster is generated with "1" primaries only
         And database "gptest" exists
         And the user create a writable external table with name "ext_test"
@@ -211,10 +200,9 @@ Feature: expand the cluster by adding more segments
 
     @gpexpand_icw_db_concourse
     Scenario: Use a dump of the ICW database for expansion
-        Given a working directory of the test as '/data/gpdata/gpexpand'
-        And the database is killed on hosts "mdw,sdw1,sdw2,sdw3"
+        Given the database is not running
+        And a working directory of the test as '/data/gpdata/gpexpand'
         And a temporary directory under "/data/gpdata/gpexpand/expandedData" to expand into
-        And the database is not running
         And a cluster is created with mirrors on "mdw" and "sdw1"
         And database "gptest" exists
         And the user runs psql with "-f /home/gpadmin/sqldump/dump.sql" against database "gptest"
@@ -230,11 +218,10 @@ Feature: expand the cluster by adding more segments
     @gpexpand_no_restart
     @gpexpand_catalog_copied
     Scenario: expand a cluster without restarting db and catalog has been copied
-        Given a working directory of the test as '/data/gpdata/gpexpand'
-        And the database is killed on hosts "mdw,sdw1"
+        Given the database is not running
+        And a working directory of the test as '/data/gpdata/gpexpand'
         And the user runs command "rm -rf /data/gpdata/gpexpand/*"
         And a temporary directory under "/data/gpdata/gpexpand/expandedData" to expand into
-        And the database is not running
         And a cluster is created with no mirrors on "mdw" and "sdw1"
         And the master pid has been saved
         And database "gptest" exists
@@ -255,11 +242,10 @@ Feature: expand the cluster by adding more segments
     @gpexpand_no_restart
     @gpexpand_conf_copied
     Scenario: expand a cluster without restarting db and conf has been copie
-        Given a working directory of the test as '/data/gpdata/gpexpand'
-        And the database is killed on hosts "mdw,sdw1"
+        Given the database is not running
+        And a working directory of the test as '/data/gpdata/gpexpand'
         And the user runs command "rm -rf /data/gpdata/gpexpand/*"
         And a temporary directory under "/data/gpdata/gpexpand/expandedData" to expand into
-        And the database is not running
         And a cluster is created with no mirrors on "mdw" and "sdw1"
         And the master pid has been saved
         And database "gptest" exists
@@ -278,11 +264,10 @@ Feature: expand the cluster by adding more segments
     @gpexpand_no_restart
     @gpexpand_long_run_read_only
     Scenario: expand a cluster without restarting db with long-run read-only transaction
-        Given a working directory of the test as '/data/gpdata/gpexpand'
-        And the database is killed on hosts "mdw,sdw1"
+        Given the database is not running
+        And a working directory of the test as '/data/gpdata/gpexpand'
         And the user runs command "rm -rf /data/gpdata/gpexpand/*"
         And a temporary directory under "/data/gpdata/gpexpand/expandedData" to expand into
-        And the database is not running
         And a cluster is created with no mirrors on "mdw" and "sdw1"
         And the master pid has been saved
         And database "gptest" exists
@@ -304,11 +289,10 @@ Feature: expand the cluster by adding more segments
     @gpexpand_no_restart
     @gpexpand_change_catalog_abort
     Scenario: expand a cluster without restarting db and any transaction which wants to change the catalog must be aborted
-        Given a working directory of the test as '/data/gpdata/gpexpand'
-        And the database is killed on hosts "mdw,sdw1"
+        Given the database is not running
+        And a working directory of the test as '/data/gpdata/gpexpand'
         And the user runs command "rm -rf /data/gpdata/gpexpand/*"
         And a temporary directory under "/data/gpdata/gpexpand/expandedData" to expand into
-        And the database is not running
         And a cluster is created with no mirrors on "mdw" and "sdw1"
         And the master pid has been saved
         And database "gptest" exists
@@ -328,11 +312,10 @@ Feature: expand the cluster by adding more segments
     @gpexpand_no_restart
     @gpexpand_dml
     Scenario: expand a cluster without restarting db and any transaction which wants to do dml work well
-        Given a working directory of the test as '/data/gpdata/gpexpand'
-        And the database is killed on hosts "mdw,sdw1"
+        Given the database is not running
+        And a working directory of the test as '/data/gpdata/gpexpand'
         And the user runs command "rm -rf /data/gpdata/gpexpand/*"
         And a temporary directory under "/data/gpdata/gpexpand/expandedData" to expand into
-        And the database is not running
         And a cluster is created with no mirrors on "mdw" and "sdw1"
         And the master pid has been saved
         And database "gptest" exists
@@ -355,11 +338,10 @@ Feature: expand the cluster by adding more segments
     @gpexpand_mirrors
     @gpexpand_rollback
     Scenario: inject a fail and test if rollback is ok
-        Given a working directory of the test as '/data/gpdata/gpexpand'
-        And the database is killed on hosts "mdw,sdw1"
+        Given the database is not running
+        And a working directory of the test as '/data/gpdata/gpexpand'
         And the user runs command "rm -rf /data/gpdata/gpexpand/*"
         And a temporary directory under "/data/gpdata/gpexpand/expandedData" to expand into
-        And the database is not running
         And a cluster is created with mirrors on "mdw" and "sdw1"
         And the user runs gpinitstandby with options " "
         And database "gptest" exists
@@ -376,11 +358,10 @@ Feature: expand the cluster by adding more segments
     @gpexpand_no_mirrors
     @gpexpand_with_special_character
     Scenario: create database,schema,table with special character
-        Given a working directory of the test as '/tmp/gpexpand_behave'
-        And the database is killed on hosts "mdw,sdw1"
+        Given the database is not running
+        And a working directory of the test as '/tmp/gpexpand_behave'
         And the user runs command "rm -rf /tmp/gpexpand_behave/*"
         And a temporary directory under "/tmp/gpexpand_behave/expandedData" to expand into
-        And the database is not running
         And a cluster is created with no mirrors on "mdw" and "sdw1"
         And database "gptest" exists
         And create database schema table with special character
@@ -397,11 +378,10 @@ Feature: expand the cluster by adding more segments
     @gpexpand_mirrors
     @gpexpand_retry_failing_work_in_phase1_after_releasing_catalog_lock
     Scenario: inject a fail and test if retry is ok
-        Given a working directory of the test as '/data/gpdata/gpexpand'
-        And the database is killed on hosts "mdw,sdw1"
+    	Given the database is not running
+        And a working directory of the test as '/data/gpdata/gpexpand'
         And the user runs command "rm -rf /data/gpdata/gpexpand/*"
         And a temporary directory under "/data/gpdata/gpexpand/expandedData" to expand into
-        And the database is not running
         And a cluster is created with mirrors on "mdw" and "sdw1"
         And the user runs gpinitstandby with options " "
         And database "gptest" exists