Reconnecting non-unique-id client

[stonier]

If a robot client gets abruptly turned off and on again, the concert will rediscover it and try to pull the list_rapps and status and invite handles, but the robot does not have a different unique id, then it will try and pull handles on top of old handles that haven't been phased out yet.

It needs to be smart enough to recognise when it is doing so and burn those old bridges before regetting them.