Set mysqlmon timeouts to 10 seconds

The backend timeouts should help prevent disconnections.

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

@@ -16,6 +16,9 @@ auto_rejoin=true
 replication_user=repl
 replication_password=repl
 ignore_external_masters=true
+backend_connect_timeout=10
+backend_read_timeout=10
+backend_write_timeout=10
 
 [RW Split Router]
 type=service