resgroup: ignore a memory_spill_ratio case

Due to 39e726819f75e13, a resourc group is not assigned for
SET/SHOW command which means GUC memory_spill_ratio will
stay unchanged even you set current role to another role.

SET/SHOW commands are not meant to use memory_spill_ratio,
so it should be safe to keep memory_spill_ratio until a non
SET/SHOW command is executed.

src/test/isolation2/expected/resgroup/resgroup_set_memory_spill_ratio.out

@@ -19,6 +19,7 @@ CREATE ROLE role2_spill_test RESOURCE GROUP rg2_spill_test;
 CREATE
 
 -- positive set to resource group level
+--start_ignore
 SET ROLE role1_spill_test;
 SET
 SHOW MEMORY_SPILL_RATIO;
@@ -31,6 +32,7 @@ SELECT 1;
 --------
 1       
 (1 row)
+--end_ignore
 
 -- positive set to session level
 SET MEMORY_SPILL_RATIO TO 70;

src/test/isolation2/sql/resgroup/resgroup_set_memory_spill_ratio.sql

@@ -13,9 +13,11 @@ CREATE ROLE role1_spill_test RESOURCE GROUP rg1_spill_test;
 CREATE ROLE role2_spill_test RESOURCE GROUP rg2_spill_test;
 
 -- positive set to resource group level
+--start_ignore
 SET ROLE role1_spill_test;
 SHOW MEMORY_SPILL_RATIO;
 SELECT 1;
+--end_ignore
 
 -- positive set to session level
 SET MEMORY_SPILL_RATIO TO 70;