fs/cifs: correctly to anonymous authentication for the NTLM(v1) authentication

fs/cifs: correctly to anonymous authentication for the NTLM(v1) authentication

commit 777f69b8d26bf35ade4a76b08f203c11e048365d upstream.

Only server which map unknown users to guest will allow
access using a non-null NTChallengeResponse.

For Samba it's the "map to guest = bad user" option.

BUG: https://bugzilla.samba.org/show_bug.cgi?id=11913

Signed-off-by: Stefan Metzmacher <metze@samba.org>
Signed-off-by: Steve French <smfrench@gmail.com>
[bwh: Backported to 3.2:
 - Adjust context, indentation
 - Keep using cERROR()]
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>