lib: gpo: Put enforced GPOs at the end of the list.

lib: gpo: Put enforced GPOs at the end of the list.

Enforced GPOs should be applied on top of all non-enforced GPOs,
so that they override policies set in non-enforced GPOs.

BUG: https://bugzilla.samba.org/show_bug.cgi?id=13046

Signed-off-by: Lutz Justen <ljusten@google.com>
Reviewed-by: Jeremy Allison <jra@samba.org>
Reviewed-by: Guenther Deschner <gd@samba.org>
Autobuild-User(master): Günther Deschner <gd@samba.org>
Autobuild-Date(master): Sat Sep 23 05:25:19 CEST 2017 on sn-devel-144

(cherry picked from commit 5f2576a9af4f3c33121ad2b27a621b5f3bb34374)