If we want to authenticate using -Wadmin@otherdomain the DC should do
take care of the authentication with the right DC for us.

BUG: https://bugzilla.samba.org/show_bug.cgi?id=13861



Pair-Programmed-With: Guenther Deschner <gd@samba.org>
Signed-off-by: Guenther Deschner <gd@samba.org>
Signed-off-by: Andreas Schneider <asn@samba.org>
Reviewed-by: Ralph Boehme <slow@samba.org>
Reviewed-by: Andrew Bartlett <abartlet@samba.org>
(cherry picked from commit 5c7f0a69)