resgroup: concourse: do not let inner ssh hijack the input.

In the resgroup concourse we use bash here doc to execute commands on
remote server, but once a ssh command is executed the preceding commands
are all ignored. This is because the here doc is hijacked or consumed by
the inner ssh.

Fixed by redirect inner ssh's stdin from /dev/null.

concourse/scripts/ic_gpdb_resgroup.bash

@@ -65,11 +65,9 @@ run_resgroup_test() {
             --disable-gpcloud --disable-gpfdist --disable-orca \
             --disable-pxf ${CONFIGURE_FLAGS}
 
-        sleep 1800
-
         make -C /home/gpadmin/gpdb_src/src/test/regress
-        ssh sdw1 mkdir -p /home/gpadmin/gpdb_src/src/test/regress
-        ssh sdw1 mkdir -p /home/gpadmin/gpdb_src/src/test/isolation2
+        ssh sdw1 mkdir -p /home/gpadmin/gpdb_src/src/test/regress </dev/null
+        ssh sdw1 mkdir -p /home/gpadmin/gpdb_src/src/test/isolation2 </dev/null
         scp /home/gpadmin/gpdb_src/src/test/regress/regress.so \
             gpadmin@sdw1:/home/gpadmin/gpdb_src/src/test/regress/