smbd: fix creation of BUILTIN\{Administrators,Users} when "tdbsam:map builtin = false"

In this case, passdb/group mapping is not responsible for the id mapping
of the builtins, so the check whether the SID maps to a unix ID is not
valid for checking whether the builtin has been created as a proper group.
So this patch changes the check to whether we find the builtin in the group
mapping database.

Signed-off-by: Michael Adam <obnox@samba.org>
Reviewed-by: Andreas Schneider <asn@samba.org>

Autobuild-User(master): Andreas Schneider <asn@cryptomilk.org>
Autobuild-Date(master): Mon May 19 16:41:41 CEST 2014 on sn-devel-104
bug #10609: CVE-2014-0239 Don't reply to replies

Due to insufficient input checking, the DNS server will reply to a packet that
has the "reply" bit set. Over UDP, this allows to send a packet with a spoofed
sender address and have two servers DOS each other with circular replies.

This patch fixes bug #10609 and adds a test to make sure we don't regress.
CVE-2014-2039 has been assigned to this issue.
Bug: https://bugzilla.samba.org/show_bug.cgi?id=10609

Signed-off-by: Kai Blin <kai@samba.org>
Reviewed-by: Stefan Metzmacher <metze@samba.org>

Autobuild-User(master): Kai Blin <kai@samba.org>
Autobuild-Date(master): Tue May 20 04:15:44 CEST 2014 on sn-devel-104