[run perf tests] Output to swarming log again.

We used to do this before
https://chromium-review.googlesource.com/c/chromium/src/+/1629432
We changed it because the swarming was cutting off the logs
because they were too long (and also loading them was difficult).

This change is a temporary trial for figuring out crbug.com/1000426
while we wait for email responses to
https://groups.google.com/a/google.com/forum/#!topic/luci-eng/3uLbRYVecuc


Bug: 1000426
Change-Id: I788d385a665604030f0df93a24e6aab3606929cd
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1790243Reviewed-by: John Chen <johnchen@chromium.org>
Commit-Queue: Caleb Rouleau <crouleau@chromium.org>
Cr-Commit-Position: refs/heads/master@{#694372}

testing/scripts/run_performance_tests.py

@@ -348,9 +348,8 @@ def execute_telemetry_benchmark(
       return_code = xvfb.run_executable(
           command, env=env, stdoutfile=output_paths.logs)
     else:
-      with open(output_paths.logs, 'w') as handle:
-        return_code = test_env.run_command_output_to_handle(
-            command, handle, env=env)
+      return_code = test_env.run_command_with_output(
+          command, env=env, stdoutfile=output_paths.logs)
     expected_results_filename = os.path.join(temp_dir, 'test-results.json')
     if os.path.exists(expected_results_filename):
       shutil.move(expected_results_filename, output_paths.test_results)