MB-11072 Don't check the expiration time for temp items.

We don't need to check the expiration time for temp items when
we fetch an item from the hash table.

Change-Id: I627eb296bedf48fa2868e838ac787fb03e54eb08
Reviewed-on: http://review.couchbase.org/37075
Reviewed-by: Michael Wiederhold <mike@couchbase.com>
Reviewed-by: Sundararaman Sridharan <sundar@couchbase.com>
Tested-by: Chiyoung Seo <chiyoung@couchbase.com>