vp9: Adjust key-frame pars in vpx_temporal_svc_encoder.
vp9: Adjust key-frame pars in vpx_temporal_svc_encoder.

Sample encoder change: reduce max-intra-rate to 1000 and
buf-initial to 600. Paramaters affect target size of key frame.

Change-Id: I2be6bc2927f5fa74e19e1efa3fb574d23a503300

ShiftMediaProject/libvpx,ShiftMediaProject/libvpx,ShiftMediaProject/libvpx,webmproject/libvpx,webmproject/libvpx,ShiftMediaProject/libvpx,webmproject/libvpx,webmproject/libvpx,webmproject/libvpx,ShiftMediaProject/libvpx,webmproject/libvpx