Banjax should pass an error to the user when origin is down

[nosmo]

When ATS receives an ERR_CONNECT_FAIL from the origin server, Banjax does not return a 400 or 500 error, it simply hangs leaving the user with an unterminated connection. On a really bad day this could increase server load, but it at the very least leaves users annoyed and blaming Deflect because the spinning logo may stick around instead of loading a blank page (which also happens in some browsers).