s3/utils: fix regression where specifying -Unetbios/root works

s3/utils: fix regression where specifying -Unetbios/root works

Usually you need to be root on a linux server to modify quotas. Even
with a linux server joined to a windows AD you could always log in as
local root with smbcquotas. However in recent builds this has changed.
This patch fixes this

BUG: https://bugzilla.samba.org/show_bug.cgi?id=13553

Signed-off-by: Noel Power <noel.power@suse.com>
Reviewed-by: Jeremy Allison <jra@samba.org>
Autobuild-User(master): Noel Power <npower@samba.org>
Autobuild-Date(master): Tue Jul 31 19:45:59 CEST 2018 on sn-devel-144