NCBC-667: Throw AOOR at VBucket.LocatePrimary - part 3

Change-Id: I518885c34d084169c3f069a5fc6b4beb6a9c4bd8
Reviewed-on: http://review.couchbase.org/41914
Tested-by: Jeffry Morris <jeffrymorris@gmail.com>
Reviewed-by: Mark Nunberg <mnunberg@haskalah.org>