lowaudio plugin should not trigger an error when recording

[smarquard]

The lowaudio plugin from #495 sets the CA into error state if the audio drops below a threshold for a period of time.

However, this is not helpful if there's an a manual or scheduled recording underway, because it will interrupt the recording.

So the plugin should check the recorder state, and only trigger an error if the state is idle (rather than recording).

[smarquard]

Fixed locally here:

cilt-uct@36d3a26