Implement simple failover mode into mysqlmon

The mysqlmon simple failover mode allows it to direct write traffic to a
secondary node. This enables a very simple failover mode with MaxScale
when it is used in a two node master-slave setup.

server/core/config.c

@@ -185,6 +185,8 @@ static char *monitor_params[] =
     "disable_master_role_setting",
     "use_priority",
     "multimaster",
+    "failover",
+    "failcount",
     NULL
 };