alsa: ALSA devices don't stop when revid is paused

[Trek Hopton]

When a revid instance recording audio is paused, the ALSA device doesn’t stop and the lexer keeps reading 0 length data.

This is because the pool buffer needs to be closed when the ALSA device is stopped. That will trigger the buffer read to return EOF which if handled correctly will notify the revid pipeline that the input has been stopped.

[Trek Hopton]

Addressed in PR #473