CVE-2015-8467: samdb: Match MS15-096 behaviour for userAccountControl

Swapping between account types is now restricted

Bug: https://bugzilla.samba.org/show_bug.cgi?id=11552

Signed-off-by: Andrew Bartlett <abartlet@samba.org>
Reviewed-by: Jeremy Allison <jra@samba.org>
Reviewed-by: Ralph Boehme <slow@samba.org>

Autobuild-User(master): Stefan Metzmacher <metze@samba.org>
Autobuild-Date(master): Wed Dec 16 16:03:18 CET 2015 on sn-devel-104
