spoolss: retrieve published printer GUID if not in registry

spoolss: retrieve published printer GUID if not in registry

When a printer is published, the GUID for the published DN is retrieved
from the domain controller and stored in the registry.
When handling a spoolss GetPrinter(level=7) request, the same GUID is
obtained from the registry and returned to the client.

This change sees the spoolss server query the DC for the published
printer GUID if it is not present in the registry when handling a
spoolss GetPrinter(level=7) request.

BUG: https://bugzilla.samba.org/show_bug.cgi?id=11018

Pair-Programmed-With: David Disseldorp <ddiss@samba.org>
Signed-off-by: Andreas Schneider <asn@samba.org>
Signed-off-by: David Disseldorp <ddiss@samba.org>
Reviewed-by: Guenther Deschner <gd@samba.org>
Autobuild-User(master): Günther Deschner <gd@samba.org>
Autobuild-Date(master): Wed Feb 18 12:43:44 CET 2015 on sn-devel-104