Cleaning DROP TABLE which is important if the tests are run in a certain order.

This is because rpl_relayrotate.test uses InnoDB.
Example of a failing sequence:
rpl_relayrotate.test repl_user_variables.test rpl_relayrotate.test
Explaination in the files.
Btw all other tests which use InnoDB (innodb*.test) already have this final
DROP TABLE.
Removed a wrong comment of mine.

mysql-test/r/rpl_relayrotate.result

@@ -16,3 +16,4 @@ master_pos_wait('master-bin.001',3000,120)=-1
 select * from t1 where a=8000;
 a
 8000
+drop table t1;