Fix sporadic test failure in rpl_gtid_mdev4820.test

Use sync_with_master_gtid.inc instead of --sync_with_master. The latter is
not correct because the test case uses RESET MASTER; this invalidates the
existing binlog positions on the slave.

In this particular case, there was a small window where --sync_with_master
could trigger too early (on the old position), causing the test case to miss
one event.

mysql-test/suite/rpl/r/rpl_gtid_mdev4820.result

@@ -18,6 +18,7 @@ RESET MASTER;
 SET GLOBAL gtid_slave_pos= 'OLD_GTID_POS';
 include/start_slave.inc
 INSERT INTO t1 VALUES (4);
+include/save_master_gtid.inc
 SET sql_log_bin= 0;
 CALL mtr.add_suppression("The binlog on the master is missing the GTID");
 SET sql_log_bin= 1;
@@ -25,6 +26,7 @@ include/wait_for_slave_io_error.inc [errno=1236]
 STOP SLAVE SQL_THREAD;
 SET GLOBAL gtid_slave_pos= 'OLD_GTID_POS';
 include/start_slave.inc
+include/sync_with_master_gtid.inc
 SELECT * FROM t1 ORDER BY a;
 a
 1

mysql-test/suite/rpl/t/rpl_gtid_mdev4820.test

@@ -34,7 +34,7 @@ eval SET GLOBAL gtid_slave_pos= '$old_gtid_pos';
 
 --connection server_1
 INSERT INTO t1 VALUES (4);
---save_master_pos
+--source include/save_master_gtid.inc
 
 --connection server_2
 SET sql_log_bin= 0;
@@ -48,7 +48,7 @@ STOP SLAVE SQL_THREAD;
 eval SET GLOBAL gtid_slave_pos= '$old_gtid_pos';
 
 --source include/start_slave.inc
---sync_with_master
+--source include/sync_with_master_gtid.inc
 SELECT * FROM t1 ORDER BY a;
 
 --source include/stop_slave.inc