MB-11601 Check UPR_EXPIRATION message type in freeing item objects

Change-Id: I7cc345a8e7dae5dca6e16840501a81239b3d3805
Reviewed-on: http://review.couchbase.org/39004
Reviewed-by: Chiyoung Seo <chiyoung@couchbase.com>
Tested-by: Chiyoung Seo <chiyoung@couchbase.com>