More graceful maintenance mode

Currently, in case of a setup the readconnroute with router_options=master we redirect all traffic to the master. When enabling maintenance mode for this node with set server test1 maintenance, incoming connections are refused until the next monitor_interval is hit.

It would be a lot more graceful if connections are always accepted. This could be achieved by enabling maintenance mode only with the next monitoring mode. Please implement this so enabling maintenance mode is more graceful.