vp9: Scene cut/content change detection: Adjust gf update.
vp9: Scene cut/content change detection: Adjust gf update.

For 1 pass vbr mode: Increase the period of gf update on scene
cut (keep it same as orginal/default setting for now).

Change-Id: I679c3bd21152f6c4e486c8098d931c00e1d26b5f

GrokImageCompression/aom,smarter/aom,mwgoldsmith/libvpx,mbebenita/aom,ittiamvpx/libvpx-1,mwgoldsmith/vpx,luctrudeau/aom,Topopiccione/libvpx,mwgoldsmith/vpx,mwgoldsmith/libvpx,smarter/aom,ittiamvpx/libvpx-1,mwgoldsmith/vpx,webmproject/libvpx,mwgoldsmith/libvpx,luctrudeau/aom,ittiamvpx/libvpx-1,ShiftMediaProject/libvpx,GrokImageCompression/aom,ittiamvpx/libvpx-1,ShiftMediaProject/libvpx,webmproject/libvpx,luctrudeau/aom,Topopiccione/libvpx,webmproject/libvpx,mbebenita/aom,mbebenita/aom,ittiamvpx/libvpx-1,mbebenita/aom,mbebenita/aom,mbebenita/aom,mbebenita/aom,Topopiccione/libvpx,mbebenita/aom,mbebenita/aom,GrokImageCompression/aom,mwgoldsmith/vpx,smarter/aom,GrokImageCompression/aom,ShiftMediaProject/libvpx,smarter/aom,webmproject/libvpx,ShiftMediaProject/libvpx,mwgoldsmith/vpx,webmproject/libvpx,Topopiccione/libvpx,smarter/aom,ShiftMediaProject/libvpx,GrokImageCompression/aom,ittiamvpx/libvpx-1,mwgoldsmith/vpx,Topopiccione/libvpx,Topopiccione/libvpx,mwgoldsmith/libvpx,GrokImageCompression/aom,mwgoldsmith/libvpx,mwgoldsmith/libvpx,smarter/aom,luctrudeau/aom,webmproject/libvpx,luctrudeau/aom,luctrudeau/aom