CCBC-386: Remove mcserver_is_clean()

Since we're now more careful about allocating and releasing server
structures during toplogy changes, these APIs are no longer needed.

Change-Id: I3aae8784ae39fb5bdaec106930179006c32bff2d
Reviewed-on: http://review.couchbase.org/36607
Tested-by: Mark Nunberg <mnunberg@haskalah.org>
Reviewed-by: Brett Lawson <brett19@gmail.com>