run_metric should not append .html for metric name
run_metric should not append .html for metric name

Before this CL, run_metric command automatically appended ".html" to
metric search needle.
However metric_runer.RunMetric searches the metric using its
registered name in MetricRegistry, not the metric html implementation file.

This CL removes ".html" automatic append so that it can handle metric
registered without ".html" suffix.

BUG=catapult:#2095

Review URL: https://codereview.chromium.org/1828633004

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