UWP assistant sample doesn't transparently handle NoMatch, connectivity errors

[trrwilson]

This issue is for a: (mark with an x)

- [X] bug report -> please search issues before submitting
- [ ] feature request
- [ ] documentation issue or request
- [ ] regression (a behavior that used to work and stopped in a new release)

Minimal steps to reproduce

• Debug across NoMatch recognitions or Canceled events (e.g. from connection failures)
• Observe the code path and the dialog audio handling in response to these

Expected/desired behavior

• The sample doesn't make it clear that NoMatch can occur for non-keyword reasons (although it does handle audio termination) -- expected is that it demonstrates this clearly
• The sample does not appear to handle Canceled cleanly -- expected is that it does