CRAS: test_client - Add check_volume arg.
CRAS: test_client - Add check_volume arg.

check_volume is used to poll the hardware volume of the given node.

Change-Id: I48c4a52e4e92c8b228c10d885fb34ee85c45c039
Signed-off-by: Dylan Reid <c791bfe44996c1eed9c7149a0c5f12a86d58eb85@chromium.org>
Reviewed-on: https://chromium-review.googlesource.com/66668

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