MB-24034 [Ephemeral]: Fix incorrect NumDeletedItems after un-delete

MB-24034 [Ephemeral]: Fix incorrect NumDeletedItems after un-delete

In an Ephemeral bucket, if an item is created, deleted, and then
re-created, the numDeletedItem count in the SeqList is incorrect - we
fail to decrement the deleted item count when it's re-created.

Change-Id: Iba9b77be4814ebd81f252c37e4c934c65965532f
Reviewed-on: http://review.couchbase.org/77186
Tested-by: Build Bot <build@couchbase.com>
Reviewed-by: Jim Walker <jim@couchbase.com>