Problem:
========
rpl.rpl_slave_alias_replica test fails sporadically on build bot as shown
below.

rpl.rpl_slave_alias_replica 'innodb,stmt' w4 [ fail ]
+++ /usr/local/mariadb-10.5.4-linux-x86_64/mysql-test/suite/rpl/r/
rpl_slave_alias_replica.reject	2020-06-12 09:52:25.191267945 +0000
@@ -22,6 +22,7 @@
 SHOW REPLICA HOSTS;
 Server_id	Host	Port	Master_id
 2	127.0.0.1	SLAVE_PORT	1
+2	127.0.0.1	SLAVE_PORT	1

Analysis:
========
The SHOW REPLICA HOSTS command reports an additional row for the same server
occasionally. This happens because of zombie dump threads on the master.
Error log from master also confirms that "A slave with the same
server_uuid/server_id as this slave has connected to the master". Since SHOW
REPLICA HOSTS goes through the list of dump threads and reports the
corresponding hosts,the same host is reported twice.

Fix:
===
Instead of capturing the SHOW REPLICA HOSTS command in result file use
wait_show_condition.inc. This will ensure that SHOW REPLICA HOSTS command
fetches slave host details.