Use a quantizer-based threshold rather than full search for deringing

objective-1-short results (with deringing enabled):
PSNR YCbCr:      0.08%      0.03%      0.11%
   PSNRHVS:      0.06%
      SSIM:      0.12%
    MSSSIM:      0.08%
 CIEDE2000:      0.05%

Change-Id: Ifcfc42c14c33650dcf879c4d0ddd8688d4d07da1