VP9 denoiser bug-fix: artifact caused by false buffer swap.
VP9 denoiser bug-fix: artifact caused by false buffer swap.

The artifact occurs periodically when VP9 denoiser is on and
refresh_golden_frame happen. When refresh_golden_frame happen,
we should copy the frame buffer instead of swapping the pointers.

Change-Id: Ib3204c4b04db28ecf439c6d9e61f3d146f04196d

jmvalin/aom,smarter/aom,mwgoldsmith/vpx,mbebenita/aom,mbebenita/aom,mwgoldsmith/libvpx,shacklettbp/aom,ittiamvpx/libvpx-1,Topopiccione/libvpx,mbebenita/aom,Topopiccione/libvpx,ShiftMediaProject/libvpx,GrokImageCompression/aom,luctrudeau/aom,thdav/aom,ShiftMediaProject/libvpx,shacklettbp/aom,luctrudeau/aom,ittiamvpx/libvpx-1,GrokImageCompression/aom,luctrudeau/aom,thdav/aom,mbebenita/aom,smarter/aom,ShiftMediaProject/libvpx,openpeer/libvpx_new,ittiamvpx/libvpx-1,Topopiccione/libvpx,openpeer/libvpx_new,luctrudeau/aom,thdav/aom,shacklettbp/aom,ittiamvpx/libvpx-1,mbebenita/aom,mwgoldsmith/libvpx,mbebenita/aom,jmvalin/aom,mwgoldsmith/libvpx,smarter/aom,Topopiccione/libvpx,GrokImageCompression/aom,smarter/aom,jmvalin/aom,openpeer/libvpx_new,webmproject/libvpx,mwgoldsmith/vpx,jmvalin/aom,mbebenita/aom,jmvalin/aom,luctrudeau/aom,smarter/aom,mwgoldsmith/vpx,mwgoldsmith/vpx,thdav/aom,openpeer/libvpx_new,GrokImageCompression/aom,shacklettbp/aom,webmproject/libvpx,shacklettbp/aom,GrokImageCompression/aom,shacklettbp/aom,Topopiccione/libvpx,ittiamvpx/libvpx-1,thdav/aom,ShiftMediaProject/libvpx,GrokImageCompression/aom,thdav/aom,openpeer/libvpx_new,webmproject/libvpx,ittiamvpx/libvpx-1,luctrudeau/aom,mwgoldsmith/vpx,openpeer/libvpx_new,mbebenita/aom,mbebenita/aom,smarter/aom,ShiftMediaProject/libvpx,webmproject/libvpx,webmproject/libvpx,Topopiccione/libvpx,mwgoldsmith/libvpx,mwgoldsmith/libvpx,mwgoldsmith/libvpx,mwgoldsmith/vpx,jmvalin/aom,webmproject/libvpx