Fix vp9_compute_qdelta_by_rate loop behavior
Fix vp9_compute_qdelta_by_rate loop behavior

The return value from vp9_compute_qdelta_by_rate, which is
a delta value for the quantizer, could never be 0 if
(qindex == rc->worst_quality).

This occurs because target_index was setup unconditionally
in the loop and yet the loop counter stopped at
(rc->worst_quality - 1).

Change-Id: I6b59cd9b5811ff33357e71cd7d814c5e53d291f2

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