CIFS: Fix SMB2 mounts so they don't try to set or get xattrs via cifs

commit 666753c3ef8fc88b0ddd5be4865d0aa66428ac35 upstream.

When mounting with smb2 (or smb2.1 or smb3) we need to check to make
sure that attempts to query or set extended attributes do not
attempt to send the request with the older cifs protocol instead
(eventually we also need to add the support in SMB2
to query/set extended attributes but this patch prevents us from
using the wrong protocol for extended attribute operations).

Signed-off-by: Steve French <smfrench@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>