[IDEA] Refresh devices

[Tim Curtis]

Ran a quick test with a JDS Labs ODAC (port powered) and no issues.

- Plug in DAC
- Power off Pi
- Power up Pi
- Open MPD Config
- USB audio device is in dropdown list

I don't have a USB DAC with its own power switch but maybe another user with such a device can try and repro your issue.

What model DAC is it?

-Tim