Fixed race conditions in rpl_multi_update and rpl_multi_delete tests which

caused spurious test failures.

mysql-test/t/rpl_multi_delete.test

@@ -24,7 +24,7 @@ connection master;
 delete from t1;
 delete from t2;
 
-connection slave;
+sync_slave_with_master;
 # force a difference to see if master's multi-DELETE will correct it
 insert into t1 values(1);
 insert into t2 values(1);

mysql-test/t/rpl_multi_update.test

@@ -33,7 +33,7 @@ delete from t2;
 insert into t1 values(1,1);
 insert into t2 values(1,1);
 
-connection slave;
+sync_slave_with_master;
 # force a difference to see if master's multi-UPDATE will correct it
 update t1 set a=2;