vp9-svc: Set initial values for ext_buffer/flag indices.
vp9-svc: Set initial values for ext_buffer/flag indices.

Set initial values for these parameters in the vp9_init_layer_context().

This also fixes an issue in the svc-bypass mode when frame flags are
passed via the vpx_codec_encode().

Change-Id: I0968f04672f8d3d2fe2cea6b8a23f79f80d7a8b1

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