TEST DISCONNECT doesn't work for USB device

[flamme]

The TEST DISCONNECT test will listen to headset plugin event to synchronize the test with the device plugging state. That works well for a USB headset and wired headset. However, if the plugged in device is a USB DAC, it will be recognized as a USB device and will not trigger headset plugin event. In that case, the test will stuck at waiting for syncing the plugging state.