[benchmarking] Fix overall return code. Thanks Wenbin!

Handles post submission cl comment from
https://chromium-review.googlesource.com/c/chromium/src/+/1982681/5

Bug: 921353
Change-Id: If536f622a2a1d8824e1d942fccf4abc02d808a6b
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1983346
Commit-Queue: Caleb Rouleau <crouleau@chromium.org>
Commit-Queue: John Chen <johnchen@chromium.org>
Auto-Submit: Caleb Rouleau <crouleau@chromium.org>
Reviewed-by: John Chen <johnchen@chromium.org>
Cr-Commit-Position: refs/heads/master@{#727644}

testing/scripts/run_performance_tests.py

@@ -618,8 +618,9 @@ def main(sys_args):
               additional_flags=configuration['arguments'])
           output_paths = OutputFilePaths(isolated_out_dir, name).SetUp()
           print('\n### {folder} ###'.format(folder=name))
-          overall_return_code = execute_gtest_perf_test(
+          return_code = execute_gtest_perf_test(
               command_generator, output_paths, options.xvfb)
+          overall_return_code = return_code or overall_return_code
           test_results_files.append(output_paths.test_results)
     else:
       raise Exception('Telemetry tests must provide either a shard map or a '