fix(Chromecast): Silence logs about audio volume
fix(Chromecast): Silence logs about audio volume

The ChromeCast tools report any unrecognized message format, and we
receive logs about the audio volume of the cast device whenever we
send it commands. These should be ignored and not logged.

Closes #4

shaka-project/generic-webdriver-server,shaka-project/generic-webdriver-server,shaka-project/generic-webdriver-server,shaka-project/generic-webdriver-server,shaka-project/generic-webdriver-server