Fixed a PushBuild failure of the system_mysql_db test caused by the lack

of cleanups in the test case for bug33794.

mysql-test/r/subselect.result

@@ -4439,5 +4439,5 @@ GROUP BY a4;
 a4	f3	a6
 1	NULL	NULL
 2	NULL	NULL
-DROP TABLE t1, t2;
+DROP TABLE t1, t2, t3, t4;
 End of 5.0 tests.

mysql-test/t/subselect.test

@@ -3305,6 +3305,7 @@ FROM
   t2, t3, t1 JOIN t2 a1 ON t1.f9 = a1.f4
 GROUP BY a4;
 
-DROP TABLE t1, t2;
+DROP TABLE t1, t2, t3, t4;
+
 --echo End of 5.0 tests.