check all renderer mapped TrackGroups

[yuzhidi]

as MappingTrackSelectorTest#selectTracks_multipleVideoAndAudioTracks_mappedToSameRenderer defined 4 renderers, 2 video renderers two audio renderers, for better, check all renderer mapped TrackGroups

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[tonihei]

Thanks for the PR! To actually merge the change, you'd need to sign the CLA (see message above).

[tonihei]

Closing due to missing CLA.