Separate front- and back-end redirect handling

[jeffdaley]

I think the redirect problem occurs when Ember Simple Auth reports a logged-in user but the back end does not. Here are a couple important logs of a failed attempt:

// the ESA `requireAuthentication` check
[Log] afterModel isLoggedIn – true 

// the API check
[Error] Failed to load resource: the server responded with a status of 401 (Unauthorized)

That error bubbles up to the application route where we invalidate the service. At this point, the app appears to reset, as evidenced by the deprecation warning that usually only appears on appLoad.

I don't have a full grasp of Ember internals, but here's my guess: The app doesn't know what to do after invalidating the session on a protected route, so it just blows itself up. (I'd do the same.) I'm thinking that by adding a redirect back to the auth screen, we might prevent this from happening.