Time out when Phoenix is mistriggered

[pasky]

When Phoenix is errorneously triggered and there is even tiny constant background noise, it will never recover and keep listening for a query. There really should be some timeout in this phase (say, 15s) - I think this is the only major UX bug we currently have, everything else are okay glitches.

[pasky]

(This is somewhat mitigated by an exception catching fix I just pushed, which should make this condition occur much less frequently.)