CVE-2015-5370: s3:librpc/rpc: let dcerpc_check_auth() auth_{type,level} against the expected values.

BUG: https://bugzilla.samba.org/show_bug.cgi?id=11344

Signed-off-by: Stefan Metzmacher <metze@samba.org>
Reviewed-by: Günther Deschner <gd@samba.org>
