Making XID deterministic for rpl_ddl test

mysql-test/r/rpl_ddl.result:
  Making XID deterministic for test
mysql-test/t/rpl_ddl.test:
  Making XID deterministic for test

mysql-test/t/rpl_ddl.test

@@ -34,6 +34,10 @@
 ###############################################################
 # Some preparations
 ###############################################################
+# The sync_slave_with_master is needed to make the xids deterministic.
+sync_slave_with_master;
+connection master;
+
 SET AUTOCOMMIT = 1;
 #
 # 1. DROP all objects, which probably already exist, but must be created here
@@ -253,6 +257,8 @@ let $my_slave_commit= false;
 --source include/rpl_stmt_seq.inc
 
 # With prior read locking
+# Note that this test generate an error since the rpl_stmt_seq.inc
+# tries to insert into t1.
 LOCK TABLES mysqltest1.t1 READ;
 let $my_stmt= UNLOCK TABLES;
 let $my_master_commit= false;