Add more logging to dev server tests.
Add more logging to dev server tests.

Currently we have failing Canary tests that stop logging after we start
fetching the Chrome binary. Adding more logging to make it obvious if we
finish fetching it.

BUG=chromium:650838

Review-Url: https://codereview.chromium.org/2377793002

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