Fix a spurious test failure in rpl.rpl_show_slave_hosts

The test case runs SHOW SLAVE HOSTS. The output of this is only stable after
all slaves have had time to register with the master; this happens
asynchroneously.

The test was waiting for the slave with server_id=3 to appear in the output,
but it was missing a similar wait for server_id=2. Thus, if server_id=2 was
much slower to connect for some reason, it could be missing from the output,
causing the test to fail.

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

@@ -25,6 +25,11 @@ let $field= Server_id;
 # 3 is server_id of slave2.
 let $condition= ='3';
 source include/wait_show_condition.inc;
+# Make sure that the other slave also had time to register. Otherwise we get
+# occasional spurious failures where server_id=2 is missing from SHOW SLAVE
+# HOSTS, when that slave is much slower to register due to thread scheduling.
+let $condition= ='2';
+source include/wait_show_condition.inc;
 --replace_column 3 'SLAVE_PORT'
 --replace_result $SLAVE_MYPORT SLAVE_PORT $DEFAULT_MASTER_PORT DEFAULT_PORT
 SHOW SLAVE HOSTS;