vp9; Fix to unitest for high noise.
vp9; Fix to unitest for high noise.

Source if y4m, and fix comment.

Change-Id: I1eb84977d42dd0f9009c276b56b3fdb03949bfc2

webmproject/libvpx,mwgoldsmith/libvpx,mwgoldsmith/libvpx,ShiftMediaProject/libvpx,mwgoldsmith/vpx,mwgoldsmith/libvpx,mwgoldsmith/libvpx,mwgoldsmith/vpx,mwgoldsmith/vpx,mwgoldsmith/vpx,webmproject/libvpx,webmproject/libvpx,mwgoldsmith/libvpx,mwgoldsmith/vpx,webmproject/libvpx,mwgoldsmith/libvpx,ShiftMediaProject/libvpx,ShiftMediaProject/libvpx,ShiftMediaProject/libvpx,webmproject/libvpx,ShiftMediaProject/libvpx,mwgoldsmith/vpx,webmproject/libvpx