MB-10118 Eliminate old _all_docs.

Change-Id: I374c0a4cbd747efe9c48223c772a957f69c4f80a
Reviewed-on: http://review.couchbase.org/34753
Reviewed-by: Artem Stemkovski <artem@couchbase.com>
Tested-by: Artem Stemkovski <artem@couchbase.com>