Don't expose load_user_db().. use cbsas_refresh() instead

Change-Id: Ie7f018382493901115dd2286a771255b57a38acf
Reviewed-on: http://review.couchbase.org/28653
Tested-by: Trond Norbye <trond.norbye@gmail.com>
Reviewed-by: Michael Wiederhold <mike@couchbase.com>