Users of the CADI library should be able to detect AAF service down

As a user of the CADI library, I want to be able to get better information about the state of the AAF service. If CADI only returns boolean authorized/unauthorized with no information about the status of the connection to AAF, client applications cannot report accurately whether the authorization indeed failed or if the authorization service is unavailable. We would prefer to return 503 instead of 403 in the event of an AAF system failure.