MDEV-15393 post-push: complete rpl_mysqldump_gtid_slave_pos fixes.

Added a missed
  --source include/save_master_gtid.inc
by the previous commit.

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

@@ -30,6 +30,7 @@ insert into t1 set a = 4;
 insert into t1 set a = 3;
 insert into t1 set a = 2;
 insert into t1 set a = 1;
+include/save_master_gtid.inc
 connection slave;
 CHANGE MASTER TO master_use_gtid= no;
 include/start_slave.inc

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

@@ -44,6 +44,7 @@ while ($i)
   eval insert into t1 set a = $i;
   --dec $i
 }
+--source include/save_master_gtid.inc
 
 --connection slave
 # due to MDEV-19801 on 10+.10+