MB-23211: Allow the expiry callback to carry full item

MB-23211: Allow the expiry callback to carry full item

The expiry callback needs to carry the whole item so that in the
case of full eviction, the system xattrs can be retained in the
body after deleting the rest of the body

Change-Id: Id3cb613217f4882a0f0400c01318bb2efc58b8aa
Reviewed-on: http://review.couchbase.org/75861
Tested-by: Build Bot <build@couchbase.com>
Reviewed-by: Dave Rigby <daver@couchbase.com>