Set second ref frame to be NONE in key frame coding
Set second ref frame to be NONE in key frame coding

This commit explicitly set the second reference frame type to be
NONE in key frame coding mode. This fixes a subtle dependency of
reference motion vector used by next inter frame on mode_info
reset before key frame coding.

Change-Id: I5ff0359753fdc9992b0bfe889490f7a32d7d5f6a

thdav/aom,smarter/aom,reimaginemedia/webm.libvpx,felipebetancur/libvpx,Suvarna1488/webm.libvpx,thdav/aom,shacklettbp/aom,luctrudeau/aom,openpeer/libvpx_new,thdav/aom,matanbs/webm.libvpx,charup/https---github.com-webmproject-libvpx-,iniwf/webm.libvpx,Distrotech/libvpx,kleopatra999/webm.libvpx,openpeer/libvpx_new,Laknot/libvpx,abwiz0086/webm.libvpx,mwgoldsmith/vpx,zofuthan/libvpx,smarter/aom,jdm/libvpx,webmproject/libvpx,lyx2014/libvpx_c,charup/https---github.com-webmproject-libvpx-,Acidburn0zzz/webm.libvpx,goodleixiao/vpx,altogother/webm.libvpx,mbebenita/aom,shyamalschandra/libvpx,shareefalis/libvpx,Distrotech/libvpx,felipebetancur/libvpx,jdm/libvpx,ShiftMediaProject/libvpx,iniwf/webm.libvpx,Topopiccione/libvpx,Maria1099/webm.libvpx,shacklettbp/aom,shyamalschandra/libvpx,mbebenita/aom,matanbs/vp982,mwgoldsmith/vpx,pcwalton/libvpx,lyx2014/libvpx_c,pcwalton/libvpx,mwgoldsmith/vpx,mwgoldsmith/vpx,gshORTON/webm.libvpx,gshORTON/webm.libvpx,kleopatra999/webm.libvpx,abwiz0086/webm.libvpx,Acidburn0zzz/webm.libvpx,matanbs/vp982,zofuthan/libvpx,jdm/libvpx,webmproject/libvpx,kalli123/webm.libvpx,ittiamvpx/libvpx-1,mbebenita/aom,kim42083/webm.libvpx,Suvarna1488/webm.libvpx,altogother/webm.libvpx,hsueceumd/test_hui,zofuthan/libvpx,mbebenita/aom,openpeer/libvpx_new,GrokImageCompression/aom,shareefalis/libvpx,shacklettbp/aom,gshORTON/webm.libvpx,iniwf/webm.libvpx,GrokImageCompression/aom,Topopiccione/libvpx,Distrotech/libvpx,luctrudeau/aom,Laknot/libvpx,hsueceumd/test_hui,kim42083/webm.libvpx,ittiamvpx/libvpx-1,luctrudeau/aom,stewnorriss/libvpx,hsueceumd/test_hui,goodleixiao/vpx,kalli123/webm.libvpx,kim42083/webm.libvpx,jacklicn/webm.libvpx,reimaginemedia/webm.libvpx,ShiftMediaProject/libvpx,liqianggao/libvpx,GrokImageCompression/aom,jmvalin/aom,reimaginemedia/webm.libvpx,running770/libvpx,Topopiccione/libvpx,shareefalis/libvpx,VTCSecureLLC/libvpx,liqianggao/libvpx,stewnorriss/libvpx,jmvalin/aom,smarter/aom,abwiz0086/webm.libvpx,mwgoldsmith/libvpx,hsueceumd/test_hui,zofuthan/libvpx,matanbs/webm.libvpx,openpeer/libvpx_new,ittiamvpx/libvpx-1,kalli123/webm.libvpx,thdav/aom,kalli123/webm.libvpx,matanbs/webm.libvpx,running770/libvpx,pcwalton/libvpx,kleopatra999/webm.libvpx,Topopiccione/libvpx,jacklicn/webm.libvpx,shyamalschandra/libvpx,Distrotech/libvpx,shareefalis/libvpx,VTCSecureLLC/libvpx,matanbs/webm.libvpx,openpeer/libvpx_new,goodleixiao/vpx,Maria1099/webm.libvpx,goodleixiao/vpx,mbebenita/aom,kleopatra999/webm.libvpx,felipebetancur/libvpx,luctrudeau/aom,liqianggao/libvpx,ShiftMediaProject/libvpx,pcwalton/libvpx,GrokImageCompression/aom,webmproject/libvpx,altogother/webm.libvpx,gshORTON/webm.libvpx,pcwalton/libvpx,jacklicn/webm.libvpx,jmvalin/aom,shyamalschandra/libvpx,kleopatra999/webm.libvpx,Suvarna1488/webm.libvpx,abwiz0086/webm.libvpx,charup/https---github.com-webmproject-libvpx-,matanbs/vp982,mwgoldsmith/libvpx,jmvalin/aom,webmproject/libvpx,stewnorriss/libvpx,goodleixiao/vpx,mbebenita/aom,mbebenita/aom,ShiftMediaProject/libvpx,Topopiccione/libvpx,hsueceumd/test_hui,Acidburn0zzz/webm.libvpx,mbebenita/aom,lyx2014/libvpx_c,mwgoldsmith/libvpx,pcwalton/libvpx,jacklicn/webm.libvpx,felipebetancur/libvpx,abwiz0086/webm.libvpx,Suvarna1488/webm.libvpx,jdm/libvpx,Laknot/libvpx,smarter/aom,lyx2014/libvpx_c,shacklettbp/aom,openpeer/libvpx_new,GrokImageCompression/aom,liqianggao/libvpx,Suvarna1488/webm.libvpx,hsueceumd/test_hui,Maria1099/webm.libvpx,shareefalis/libvpx,iniwf/webm.libvpx,reimaginemedia/webm.libvpx,ittiamvpx/libvpx-1,Distrotech/libvpx,matanbs/vp982,ShiftMediaProject/libvpx,VTCSecureLLC/libvpx,kim42083/webm.libvpx,Laknot/libvpx,Acidburn0zzz/webm.libvpx,charup/https---github.com-webmproject-libvpx-,mwgoldsmith/libvpx,iniwf/webm.libvpx,matanbs/vp982,jdm/libvpx,lyx2014/libvpx_c,lyx2014/libvpx_c,stewnorriss/libvpx,mwgoldsmith/vpx,matanbs/webm.libvpx,Acidburn0zzz/webm.libvpx,goodleixiao/vpx,Maria1099/webm.libvpx,gshORTON/webm.libvpx,charup/https---github.com-webmproject-libvpx-,ittiamvpx/libvpx-1,mwgoldsmith/libvpx,Acidburn0zzz/webm.libvpx,jmvalin/aom,smarter/aom,running770/libvpx,altogother/webm.libvpx,mwgoldsmith/libvpx,Laknot/libvpx,matanbs/vp982,VTCSecureLLC/libvpx,charup/https---github.com-webmproject-libvpx-,webmproject/libvpx,zofuthan/libvpx,jacklicn/webm.libvpx,running770/libvpx,VTCSecureLLC/libvpx,mbebenita/aom,shyamalschandra/libvpx,shacklettbp/aom,ittiamvpx/libvpx-1,kalli123/webm.libvpx,felipebetancur/libvpx,luctrudeau/aom,matanbs/webm.libvpx,reimaginemedia/webm.libvpx,kim42083/webm.libvpx,altogother/webm.libvpx,stewnorriss/libvpx,jdm/libvpx,shareefalis/libvpx,Maria1099/webm.libvpx,liqianggao/libvpx,mwgoldsmith/vpx,thdav/aom,Maria1099/webm.libvpx,webmproject/libvpx,thdav/aom,iniwf/webm.libvpx,altogother/webm.libvpx,stewnorriss/libvpx,Topopiccione/libvpx,jacklicn/webm.libvpx,felipebetancur/libvpx,VTCSecureLLC/libvpx,running770/libvpx,shacklettbp/aom,Suvarna1488/webm.libvpx,Distrotech/libvpx,luctrudeau/aom,liqianggao/libvpx,abwiz0086/webm.libvpx,jmvalin/aom,zofuthan/libvpx,kalli123/webm.libvpx,gshORTON/webm.libvpx,kleopatra999/webm.libvpx,smarter/aom,matanbs/vp982,kim42083/webm.libvpx,Laknot/libvpx,GrokImageCompression/aom,reimaginemedia/webm.libvpx,shyamalschandra/libvpx,running770/libvpx