Revert "Merge "Change highbd variance rounding to prevent negative variance."" This reverts commit ea48370a500537906d62544ca4ed75301d79e772, reversing changes made to 15939cb2d76c773950cda40988ede89e111872ea. The commit was insufficiently tested and causes failures. Change-Id: I623d6fc2cd3ae6fd42d0abab1f8eada465ae57a7