Fixed mtr random bug in lock_sync.test

mysql-test/main/lock_sync.result

@@ -900,6 +900,6 @@ set debug_sync= 'now wait_for s1';
 SELECT * FROM ( SELECT * FROM v1 ) sq;
 COMMIT;
 DROP VIEW v1;
-DROP FUNCTION f;
+DROP FUNCTION IF EXISTS f;
 DROP TABLE t1, t2;
 set debug_sync= 'reset';

mysql-test/main/lock_sync.test

@@ -1219,6 +1219,6 @@ COMMIT;
 --disconnect con2
 --connection default
 DROP VIEW v1;
-DROP FUNCTION f;
+DROP FUNCTION IF EXISTS f;
 DROP TABLE t1, t2;
 set debug_sync= 'reset';