PocketPOD: auto-detect or test may leave app hanging

[arteme]

The PocketPOD driver is known to be buggy and closing MIDI on Windows when PocketPOD is sending data will hard-hang the app. This was worked around for in application exit (or main MIDI thread handling) in #12. However, "test" and "autodetect", when ran through the settings dialog, may close the MIDI device too early triggering the same hang.