message: Add backwards compatibilty to peer codecs config.
  This is a small follow-up to
  in order to make
  the switch incremental.
  No-Try: True
  Cr-Commit-Position: refs/heads/master@{#34478}
diff: @@ -100,6 +100,9 @@ void SetDefaultValuesForMissingParams(
  p->video_codecs.push_back(
  PeerConnectionE2EQualityTestFixture::VideoCodecConfig(
  cricket::kVp8CodecName));
  + run_params->video_codecs = {
  + PeerConnectionE2EQualityTestFixture::VideoCodecConfig(
  + cricket::kVp8CodecName)};
  }
  } else {
  RTC_CHECK(run_params->video_codecs.empty())
  