Bug#38540 rpl_server_id2 uses show slave status unnecessarily

a minor improvement to the test to ease merging.

mysql-test/suite/rpl/r/rpl_server_id2.result

@@ -20,7 +20,7 @@ reset master;
 create table t1(n int);
 create table t2(n int);
 change master to master_port=MASTER_PORT;
-start slave until master_log_file='master-bin.000001', master_log_pos=107;
+start slave until master_log_file='master-bin.000001', master_log_pos=UNTIL_POS;
 *** checking until postion execution: must be only t1 in the list ***
 show tables;
 Tables_in_test

mysql-test/suite/rpl/t/rpl_server_id2.test

@@ -42,6 +42,7 @@ create table t2(n int);
 connection slave;
 --replace_result $MASTER_MYPORT MASTER_PORT
 eval change master to master_port=$MASTER_MYPORT;
+--replace_result $until_pos UNTIL_POS
 eval start slave until master_log_file='master-bin.000001', master_log_pos=$until_pos;
 --source include/wait_for_slave_io_to_start.inc
 --source include/wait_for_slave_sql_to_stop.inc