[Telemetry] Un-break help command

This CL fixes the help command of benchmark_runner, which broke after the local
environment switch.

R=dtu,nednguyen

Review URL: https://codereview.chromium.org/979573002

Cr-Commit-Position: refs/heads/master@{#318976}

tools/telemetry/telemetry/benchmark_runner.py

@@ -68,7 +68,7 @@ class Help(command_line.OptparseCommand):
       if len(commands) == 1:
         command = commands[0]
         parser = command.CreateParser()
-        command.AddCommandLineArgs(parser)
+        command.AddCommandLineArgs(parser, None)
         parser.print_help()
         return 0