CRAS: audio_thread - Log state of each stream when writing.

Log when data is fetched form playback streams and log each stream
when writing audio data.

BUG=none
TEST=run and check log.

Signed-off-by: Dylan Reid <dgreid@chromium.org>
Change-Id: Ib9fe5f89001ec33cc2033ebea99f47c2a8759369
Reviewed-on: https://chromium-review.googlesource.com/188964
Reviewed-by: Hsinyu Chao <hychao@chromium.org>