init_providers: disable providers not explicitly active

Change-Id: I8cccb1beaa03f4c4a48c536c34502c5afcf99d29
Reviewed-on: http://review.couchbase.org/35249
Reviewed-by: Brett Lawson <brett19@gmail.com>
Tested-by: Mark Nunberg <mnunberg@haskalah.org>
Reviewed-on: http://review.couchbase.org/36418