[telemetry] Fix bad serial log filename specification in BattOrWrapper
[telemetry] Fix bad serial log filename specification in BattOrWrapper

TBR=nednguyen@google.com
BUG=catapult:#2638

Review-Url: https://codereview.chromium.org/2254573002

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