Proper cleanup for BDB test

mysql-test/r/bdb_cache.result:
  Results fixed
mysql-test/t/bdb_cache.test:
  Add proper cleanup for the 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

@@ -48,3 +48,4 @@ show status like "Qcache_queries_in_cache";
 show status like "Qcache_hits";
 commit;
 show status like "Qcache_queries_in_cache";
+drop table if exists t1, t2, t3;