MB-7522 Do updater restarts if a pending transition exists

So that we don't dive into too much complex state transitions.

Change-Id: I4314018838ea20e804e087960bb533e34c397f12
Reviewed-on: http://review.couchbase.org/24014
Tested-by: Filipe David Borba Manana <fdmanana@gmail.com>
Reviewed-by: Volker Mische <volker.mische@gmail.com>