Fixed encoder crash when mult-threading is enabled.

Happens in real-time mode.  Will happen in good quality, speed 1.

Change-Id: I3e5b68827b1a5798d0431b088a709256d1ce2c95

vp8/encoder/ethreading.c

@@ -310,6 +310,7 @@ static void setup_mbby_copy(MACROBLOCK *mbdst, MACROBLOCK *mbsrc)
     for (i = 0; i < 25; i++)
     {
         z->block[i].quant           = x->block[i].quant;
+        z->block[i].quant_fast      = x->block[i].quant_fast;
         z->block[i].quant_shift     = x->block[i].quant_shift;
         z->block[i].zbin            = x->block[i].zbin;
         z->block[i].zrun_zbin_boost   = x->block[i].zrun_zbin_boost;