CVE-2015-5370: s4:rpc_server: let a failing auth3 mark the authentication as invalid

Following requests will generate a fault with ACCESS_DENIED.

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>
