fs/cifs: correctly to anonymous authentication for the NTLM(v2) authentication

fs/cifs: correctly to anonymous authentication for the NTLM(v2) authentication

commit 1a967d6c9b39c226be1b45f13acd4d8a5ab3dc44 upstream.

Only server which map unknown users to guest will allow
access using a non-null NTLMv2_Response.

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>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>