[perf/contrib] Fix option validation in loading_ct benchmarks

Running the command, e.g.:

$ tools/perf/run_benchmark loading.cluster_telemetry --browser stable

Used to fail with an exception. Now instead prints a more user friendly
error message:

    Usage: run_benchmark run benchmark_name [<options>]

    run_benchmark: error: Please specify --user-agent.

Bug: 1009012
Change-Id: Id3b3ba521f3aa10b98a8e7a6aeae52c6f5cd8e5a
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1872103
Commit-Queue: Juan Antonio Navarro Pérez <perezju@chromium.org>
Commit-Queue: Ravi Mistry <rmistry@chromium.org>
Auto-Submit: Juan Antonio Navarro Pérez <perezju@chromium.org>
Reviewed-by: Ravi Mistry <rmistry@chromium.org>
Cr-Commit-Position: refs/heads/master@{#708181}

tools/perf/contrib/cluster_telemetry/loading_base_ct.py

@@ -36,6 +36,10 @@ class _LoadingBaseClusterTelemetry(loading._LoadingBase):
         help='Cache temperature (string). Default to "%%default". Can be: %s' %
          ', '.join(cls._ALL_CACHE_TEMPERATURES))
 
+  @classmethod
+  def ProcessCommandLineArgs(cls, parser, args):
+    ct_benchmarks_util.ValidateCommandLineArgs(parser, args)
+
   def CreateStorySet(self, options):
     def Wait(action_runner):
       action_runner.Wait(options.wait_time)