vp8: Update on sum_diff_threshold.
vp8: Update on sum_diff_threshold.

Reset to previous values.

Change-Id: Ia49bafc1d1ec5f657819ffba04d11fd701f315e8

GrokImageCompression/aom,mwgoldsmith/libvpx,mbebenita/aom,GrokImageCompression/aom,ShiftMediaProject/libvpx,GrokImageCompression/aom,luctrudeau/aom,webmproject/libvpx,mbebenita/aom,Topopiccione/libvpx,mwgoldsmith/vpx,mwgoldsmith/libvpx,mwgoldsmith/vpx,GrokImageCompression/aom,luctrudeau/aom,mbebenita/aom,Topopiccione/libvpx,luctrudeau/aom,ShiftMediaProject/libvpx,mwgoldsmith/vpx,luctrudeau/aom,ShiftMediaProject/libvpx,mwgoldsmith/libvpx,smarter/aom,mwgoldsmith/libvpx,smarter/aom,Topopiccione/libvpx,Topopiccione/libvpx,mbebenita/aom,mwgoldsmith/vpx,Topopiccione/libvpx,mwgoldsmith/vpx,mbebenita/aom,smarter/aom,mwgoldsmith/libvpx,GrokImageCompression/aom,webmproject/libvpx,mbebenita/aom,webmproject/libvpx,Topopiccione/libvpx,webmproject/libvpx,mbebenita/aom,smarter/aom,luctrudeau/aom,ShiftMediaProject/libvpx,mwgoldsmith/libvpx,webmproject/libvpx,mwgoldsmith/vpx,ShiftMediaProject/libvpx,mbebenita/aom,webmproject/libvpx,smarter/aom,luctrudeau/aom,mbebenita/aom,GrokImageCompression/aom,smarter/aom