Set schema back from non-default at end of test

Since the PG connection is reused, leaving it test2 could cause random failures in later tests that include a schema name.

These failures happen much more often after https://github.com/MMcM/sql-layer/commit/64b4a58d291743971c7ef545b48108f3aae80a99#diff-5baeb7c3e74230b91803cd2c023eb8feR103, which fixes an explicit schema getting lost after any DDL.