s3:winbindd: let wb_irpc_SamLogon reject the local domain as RWDC

s3:winbindd: let wb_irpc_SamLogon reject the local domain as RWDC

If the clients use a subdomain of our domain the
'sam' auth backend passed the request along to
the 'winbind' auth backend. If winbindd tries
to use the local domain we hit the case that
an unknown domain was used. So we need to
bounce the request back to 'sam_ignoredomain'.

BUG: https://bugzilla.samba.org/show_bug.cgi?id=15973

Signed-off-by: Stefan Metzmacher <metze@samba.org>
Reviewed-by: Volker Lendecke <vl@samba.org>
Autobuild-User(master): Volker Lendecke <vl@samba.org>
Autobuild-Date(master): Tue Apr 28 11:49:16 UTC 2026 on atb-devel-224