vp9: refactor vp9 datarate test for better sharding.
vp9: refactor vp9 datarate test for better sharding.

Change-Id: Icfaf29e1ca847ba9e3748700c9e09383ce8d1f65

webmproject/libvpx,webmproject/libvpx,ShiftMediaProject/libvpx,webmproject/libvpx,webmproject/libvpx,webmproject/libvpx,ShiftMediaProject/libvpx,ShiftMediaProject/libvpx,ShiftMediaProject/libvpx,ShiftMediaProject/libvpx,webmproject/libvpx