s3-winbindd: Fix internal winbind dsgetdcname calls w.r.t. domain name

s3-winbindd: Fix internal winbind dsgetdcname calls w.r.t. domain name

when winbind calls to dsgetdcname internally, make sure to
prefer the DNS domain name if we have it. Makes DNS lookups much more
likely to succeed.

BUG: https://bugzilla.samba.org/show_bug.cgi?id=15876

Guenther

Signed-off-by: Guenther Deschner <gd@samba.org>
Reviewed-by: Andreas Schneider <asn@samba.org>
Reviewed-by: Ralph Boehme <slow@samba.org>
Autobuild-User(master): Ralph Böhme <slow@samba.org>
Autobuild-Date(master): Mon Jul  7 10:44:37 UTC 2025 on atb-devel-224