variance_test partial clean-up
variance_test partial clean-up

remove some (but not all yet!) tuple mis-use, and revamp the code a lot.
Factorize some common chores into MainTestClass.

Change-Id: Ia14f3924140e8545e4f10d0504475681baae8336

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