Fix to setting incorrect rev_seqno in hashtable::add()

If an item in hashtable has a state of temp_deleted_key, which
means that the item is marked as "deleted" in a storage layer,
we should set its rev_seqno to its current rev_seqno + 1
when that item is added back to the hashtable.

Change-Id: I9671a7826b9d9302d04d86f84cf1a8e502a5e912
Reviewed-on: http://review.couchbase.org/33167
Reviewed-by: Chiyoung Seo <chiyoung@couchbase.com>
Tested-by: Chiyoung Seo <chiyoung@couchbase.com>