Revert to Previous Peer De-registration Behavior

The quandry is what to do with peers that have disappeared for too
long. If we keep trying to re-register, we could be quite busy doing
that for an eternity… but if we de-reg the peer and it comes back in 10
minutes, but, say, never lost the master, we don’t get a peer list for
a LONG time and we don’t get it back then either…. There’s no good
answer right now. Anyone got one?