Bug#36818: rpl_server_id1 fails expecting slave has stopped

The test is vulnerable because it does not check if slave has stopped at time
of the new session is requested `start slave;'

Fixed with deploying explicitly wait_for_slave_to_stop synchronization macro.

mysql-test/suite/rpl/t/rpl_server_id1.test

@@ -10,6 +10,7 @@ reset master;
 
 # replicate ourselves
 stop slave;
+source include/wait_for_slave_to_stop.inc;
 --replace_result $SLAVE_MYPORT SLAVE_PORT
 eval change master to master_port=$SLAVE_MYPORT;
 start slave;