Little fixes in the teardown sections.

Author: rzharkov

src/test/isolation/specs/snapfs_switch_to_snapshot_sequence.spec

@@ -8,7 +8,7 @@ setup {
 teardown {
 	select pg_switch_to_snapshot( 0 );
 	select pg_remove_snapshot( ( select recent_snapshot from pg_control_snapshot() ) );
-	drop sequence seq1;
+	DROP SEQUENCE IF EXISTS seq1;
 }
 
 session "s1"

src/test/isolation/specs/snapfs_switch_to_snapshot_three_backends.spec

@@ -14,7 +14,7 @@ teardown
 {
  select pg_switch_to_snapshot( 0 );
  select pg_remove_snapshot( ( select recent_snapshot from pg_control_snapshot() ) );
- DROP TABLE t1;
+ DROP TABLE IF EXISTS t1;
 }
 
 session "s1"

src/test/isolation/specs/snapfs_vacuum_table.spec

@@ -11,7 +11,7 @@ setup {
 teardown {
  select pg_switch_to_snapshot( 0 );
  select pg_remove_snapshot( ( select recent_snapshot from pg_control_snapshot() ) );
- DROP TABLE t1;
+ DROP TABLE IF EXISTS t1;
 }
 
 session "s1"

src/test/isolation/specs/snapfs_view.spec

@@ -11,7 +11,7 @@ setup {
 teardown {
  select pg_switch_to_snapshot( 0 );
  select pg_remove_snapshot( ( select recent_snapshot from pg_control_snapshot() ) );
- DROP TABLE t1 CASCADE;
+ DROP TABLE IF EXISTS t1 CASCADE;
 }
 
 session "s1"