Modified resize loop constraints.
Using a tighter resize constraint on undershoot seems to help
results (especially SSIM) as significant undershoot on a frame
seems to have more of a damaging impact than overshoot.
This patch has been tuned so that in local testing using the
derf set it is encode speed neutral for speed setting 2.
Average quality result for speed 2 (psnr,ssim) were as follows:-
lowres 0.039, 0.453
midres 0.249, 0.853
hdres 0.159, 0.659
NetFlix -0.241, 0.360
Change-Id: Ie8d3a0d7d6f7ea89d9965d1821be17f8bda85062