CRAS: audio_thread - Add an event log.

Log certain interesting events that happen in the audio thread, add this
log to audio debug info.  Change the test client to print this log when
dumping audio info.

Change-Id: I1b93cfd36731f2ee8b6700faba44fb36ead161e6
Signed-off-by: Dylan Reid <dgreid@chromium.org>
CRAS: audio_thread - Handle EINTR when waiting for streams.

If there select call in interrupted, retry it.  If there is an error
other than EINTR, break out of the waiting loop.

BUG=none
TEST=none

Change-Id: I3762ee6dca039a24236222dd6cb7df2f3bef44d7
Signed-off-by: Dylan Reid <dgreid@chromium.org>