s4:kdc: disable support for CROSS_ORGANIZATION domains

s4:kdc: disable support for CROSS_ORGANIZATION domains

We don't support selective authentication yet,
so we shouldn't silently allow domain wide authentication
for such a trust.

BUG: https://bugzilla.samba.org/show_bug.cgi?id=13299

Signed-off-by: Stefan Metzmacher <metze@samba.org>
Reviewed-by: Ralph Boehme <slow@samba.org>
Autobuild-User(master): Stefan Metzmacher <metze@samba.org>
Autobuild-Date(master): Wed Feb 28 19:45:13 CET 2018 on sn-devel-144

(cherry picked from commit 31b5328c46c5f510ba234f75688886987276ee9e)

Autobuild-User(v4-8-test): Stefan Metzmacher <metze@samba.org>
Autobuild-Date(v4-8-test): Thu Mar  1 06:08:56 CET 2018 on sn-devel-144