Proper cleanup for BDB test

mysql-test/r/bdb_cache.result

@@ -98,3 +98,4 @@ commit;
 show status like "Qcache_queries_in_cache";
 Variable_name	Value
 Qcache_queries_in_cache	1
+drop table if exists t1, t2, t3;

mysql-test/t/bdb_cache.test

@@ -47,4 +47,5 @@ select * from t3;
 show status like "Qcache_queries_in_cache";
 show status like "Qcache_hits";
 commit;
-show status like "Qcache_queries_in_cache";
\ No newline at end of file
+show status like "Qcache_queries_in_cache";
+drop table if exists t1, t2, t3;