vp9 non-rd pickmode. Some adjustments for vbr mode.

Some adjustments to inter-mode selection for vbr mode.
Condition some of the bias to low/zero motion on cbr mode, and
don't use int_pro_motion_estimation for golden ref
(treat it same as last ref).

Change only affect 1 pass vbr mode, speed >=5 (non-rd pickmode).

Encoding time increase within ~5%.
Avg PSNR/SSIM on RTC set increase by ~2%, all clips up,
ranging from 0.5 to 4%.

Change-Id: I0048d0104a8816773d91a2b1484d601169d9bad7
1 file changed