Fix flaky advisory lock test.
Fix flaky advisory lock test.

Random failures due to active connection checking within the
assert_no_changes block.

Failure:
MigrationTest#test_with_advisory_lock_closes_connection [/rails/activerecord/test/cases/migration_test.rb:947]:
--- expected
+++ actual
@@ -1 +1 @@
-["SELECT 1", "SELECT 1"]
+["SELECT 1", "SELECT 1", "SELECT 1"]

This commit scopes the query down further to ensure that the advisory
unlock query is not left in pg_stat_activity which is an indication that
the connection pool was not disconnected.

Edouard-chin/rails,schuetzm/rails,rails/rails,Edouard-chin/rails,Envek/rails,georgeclaghorn/rails,bogdanvlviv/rails,yawboakye/rails,BlakeWilliams/rails,kddeisz/rails,esparta/rails,vipulnsward/rails,schuetzm/rails,georgeclaghorn/rails,yahonda/rails,yawboakye/rails,Edouard-chin/rails,Edouard-chin/rails,Envek/rails,Vasfed/rails,eileencodes/rails,lcreid/rails,lcreid/rails,BlakeWilliams/rails,kmcphillips/rails,yawboakye/rails,Stellenticket/rails,MSP-Greg/rails,betesh/rails,vipulnsward/rails,schuetzm/rails,vipulnsward/rails,BlakeWilliams/rails,EmmaB/rails-1,lcreid/rails,joonyou/rails,eileencodes/rails,MSP-Greg/rails,Stellenticket/rails,eileencodes/rails,yalab/rails,Vasfed/rails,georgeclaghorn/rails,kddeisz/rails,MSP-Greg/rails,EmmaB/rails-1,tgxworld/rails,betesh/rails,bogdanvlviv/rails,esparta/rails,yahonda/rails,kddeisz/rails,tgxworld/rails,Envek/rails,tjschuck/rails,joonyou/rails,bogdanvlviv/rails,Vasfed/rails,tjschuck/rails,kddeisz/rails,EmmaB/rails-1,lcreid/rails,MSP-Greg/rails,schuetzm/rails,Stellenticket/rails,Erol/rails,Erol/rails,joonyou/rails,tgxworld/rails,yalab/rails,betesh/rails,tjschuck/rails,betesh/rails,Erol/rails,esparta/rails,Stellenticket/rails,tjschuck/rails,yahonda/rails,BlakeWilliams/rails,kmcphillips/rails,Envek/rails,georgeclaghorn/rails,yawboakye/rails,yalab/rails,rails/rails,eileencodes/rails,yalab/rails,kmcphillips/rails,esparta/rails,bogdanvlviv/rails,Vasfed/rails,rails/rails,rails/rails,Erol/rails,joonyou/rails,yahonda/rails,kmcphillips/rails,vipulnsward/rails,tgxworld/rails