[BattOr] Add logging to battor subprocess polling.
[BattOr] Add logging to battor subprocess polling.

I believe that crbug.com/645106 might be happening because the subprocess is stuck
polling for the RC. I am adding this logging to check if that is correct.

BUG=chromium:645106

Review-Url: https://codereview.chromium.org/2334903002

benschmaus/catapult,catapult-project/catapult-csm,catapult-project/catapult-csm,catapult-project/catapult-csm,catapult-project/catapult,benschmaus/catapult,catapult-project/catapult,sahiljain/catapult,catapult-project/catapult,benschmaus/catapult,sahiljain/catapult,catapult-project/catapult-csm,catapult-project/catapult,benschmaus/catapult,catapult-project/catapult,catapult-project/catapult,sahiljain/catapult,catapult-project/catapult,sahiljain/catapult,catapult-project/catapult-csm,sahiljain/catapult,catapult-project/catapult-csm,sahiljain/catapult,benschmaus/catapult,benschmaus/catapult,benschmaus/catapult,catapult-project/catapult-csm