Before this patch UUID update was the same as introduction of a
new member and waiting until the 'old' is dropped as 'dead' by
the failure detection component. It could take 2.5 minutes with
the default ack timeout. What is more, with GC turned off it
would always result in never deleted old UUID.

The patch on a UUID update marks the old UUID as 'left' member.
In the best and most common case it guarantees that old UUID will
be dropped not later than after 2 complete rounds, and marked as
'left' everywhere for log(cluster_size) round steps. Even with GC
turned off.

Part of #3234