Ensure we hide the establish/timeout view at the right times, and don't send hangup in timeout state

In reviewing #216 I noticed there were a couple of minor additional issues:

- On receiving an incoming call into a timed out chat window, the incoming call view would be shown, but the timed out view remained shown below it as well.
- When closing a window for a timed out call, the window would send the hangup notification, even though it had already been sent.

This PR fixes both of those.