adjusting rd constant slightly by ~10%

This is to reflect the RD improvement in the encoder. The change has a
small positive impact on quality (0.25% by VPXSSIM and 0.05% by PSNR)

Change-Id: Ic66ffc19b10870645088c0624c85556f009fd210

vp8/encoder/rdopt.c

@@ -207,7 +207,7 @@ void vp8_initialize_rd_consts(VP8_COMP *cpi, int Qvalue)
     int q;
     int i;
     double capped_q = (Qvalue < 160) ? (double)Qvalue : 160.0;
-    double rdconst = 3.00;
+    double rdconst = 2.70;
 
     vp8_clear_system_state();  //__asm emms;