MB-10277 Fix to the memory corruption bug in TOUCH command

If TOUCH command is issued with the same expiration time for
a non-resident item, it causes the segmentation fault due to
the NULL pointer to an Item instance.

This change makes sure that we create an Item instance in the
above case because we still need to send the item's metadata
to the client.

Change-Id: I5357366df05ae2e07e580093be5ac9a12a583917
Reviewed-on: http://review.couchbase.org/33846
Reviewed-by: abhinav dangeti <abhinav@couchbase.com>
Tested-by: abhinav dangeti <abhinav@couchbase.com>