Update replication-manager test

The test now checks whether replication-manager launched by a script
works. This is closer to how one of the original blog posts define the
setup.

maxscale-system-test/cnf/maxscale.cnf.template.replication_manager

@@ -12,6 +12,8 @@ monitor_interval=1000
 detect_standalone_master=true
 failcount=2
 allow_cluster_recovery=true
+events=master_down
+script=/home/vagrant/replication-manager --hosts=$LIST --user=skysql:skysql --rpluser=skysql:skysql --switchover-at-sync=false --log-level=3 --logfile=/tmp/mrm.log switchover
 
 [RW Split Router]
 type=service