Added a reset.sql to remove all the test users and databases.

test_data/reset.sql

@@ -0,0 +1,7 @@
+DROP USER epgsql_test;
+DROP USER epgsql_test_md5;
+DROP USER epgsql_test_cleartext;
+DROP USER epgsql_test_cert;
+
+DROP DATABASE epgsql_test_db1;
+DROP DATABASE epgsql_test_db2;