message: perf_tests: Update perf_test_runner format.
  CL#14740 modified the result format but
  the test runner script was never updated.
  This fixes the result format and metric check.
diff: @@ -115,9 +115,9 @@ def get_results(metric, extra_args=[]):
  print(output)
  sys.exit(3)
  - pattern = metric + r'= ([0-9.]+)'
  + pattern = metric + r'.*= ([0-9.]+)'
  m = re.findall(pattern, output)
  - if m is None:
  + if not m:
  print("Did not find the metric '%s' in the test output:" % metric)
  print(output)
  sys.exit(1)
  