Cleanup dtor code

This also decrements the newly-added 'bucket' field

Change-Id: I708aa9d81770316f8bee5ede3a95e9af01a464d5
Reviewed-on: http://review.couchbase.org/26659
Reviewed-by: Mordechai Nunberg <mnunberg@haskalah.org>
Tested-by: Mordechai Nunberg <mnunberg@haskalah.org>