BUG#13861 - START SLAVE UNTIL may stop 1 evnt too late if

            log-slave-updates and circul repl

This is a test case fix for BUG#13861.


mysql-test/r/rpl_dual_pos_advance.result:
  Fix for a test case for BUG#13861.
mysql-test/t/rpl_dual_pos_advance.test:
  Fix for a test case for BUG#13861.
  
  master_pos_wait() requires slave sql thread running. But it is not
  guaranteed for this test case. As we use start slave until it may
  execute all events and shutdown before master_pos_wait() is started.
  
  On the other hand it is safe just to wait for slave to stop here,
  as start slave returns _after_ sql thread is started.

mysql-test/r/rpl_dual_pos_advance.result

@@ -25,9 +25,6 @@ insert into t3 values(4);
 start slave until master_log_file="slave-bin.000001",master_log_pos=195;
 Warnings:
 Note	1278	It is recommended to use --skip-slave-start when doing step-by-step replication with START SLAVE UNTIL; otherwise, you will get problems if you get an unexpected slave's mysqld restart
-select master_pos_wait("slave-bin.000001",137);
-master_pos_wait("slave-bin.000001",137)
-0
 show tables;
 Tables_in_test
 t1

mysql-test/t/rpl_dual_pos_advance.test

@@ -65,12 +65,6 @@ connection master;
 # asking it to stop before creation of t3.
 
 start slave until master_log_file="slave-bin.000001",master_log_pos=195;
-
-# wait until it's started (the position below is the start of "CREATE
-# TABLE t2") (otherwise wait_for_slave_to_stop may return at once)
-
-select master_pos_wait("slave-bin.000001",137);
-
 wait_for_slave_to_stop;
 
 # then BUG#13861 causes t3 to show up below (because stopped too