aq-mode=3: Don't reset segment if block is determined to be skin.

For coding block sizes <=16X16, if the block is determined to be skin,
then always allow for that block to be candidate for refresh. So if that
block happens to be on the boost segment(s), segment won't get reset to 0
and delta-q will be applied.

PSNR/SSIM metrics neutral (little/no change) on RTC clips.
Speed increase small/negligible (< 1%).
Some visual improvement on faces in a few RTC clips.

Change-Id: I6bf0fce6f39d820b491ce05d7c017ad168fce7d6