Fix incorrect logic in run_dev_server
Fix incorrect logic in run_dev_server

R=dsinclair@chromium.org

Review URL: https://codereview.appspot.com/251290043 .

0x90sled/catapult,catapult-project/catapult-csm,catapult-project/catapult,scottmcmaster/catapult,catapult-project/catapult,sahiljain/catapult,catapult-project/catapult,danbeam/catapult,benschmaus/catapult,SummerLW/Perf-Insight-Report,SummerLW/Perf-Insight-Report,modulexcite/catapult,benschmaus/catapult,modulexcite/catapult,catapult-project/catapult,sahiljain/catapult,benschmaus/catapult,sahiljain/catapult,scottmcmaster/catapult,danbeam/catapult,catapult-project/catapult-csm,SummerLW/Perf-Insight-Report,catapult-project/catapult,zeptonaut/catapult,SummerLW/Perf-Insight-Report,catapult-project/catapult-csm,sahiljain/catapult,dstockwell/catapult,danbeam/catapult,catapult-project/catapult,zeptonaut/catapult,scottmcmaster/catapult,benschmaus/catapult,benschmaus/catapult,dstockwell/catapult,benschmaus/catapult,sahiljain/catapult,zeptonaut/catapult,SummerLW/Perf-Insight-Report,dstockwell/catapult,sahiljain/catapult,catapult-project/catapult,benschmaus/catapult,catapult-project/catapult-csm,catapult-project/catapult-csm,danbeam/catapult,0x90sled/catapult,modulexcite/catapult,catapult-project/catapult-csm,SummerLW/Perf-Insight-Report,dstockwell/catapult,catapult-project/catapult-csm,0x90sled/catapult