Hank Keirsey doesn’t consider himself a gamer. He talks with a slow, airline pilot drawl, believes a man should drink his whiskey neat, and uses a bow with a 65-pound draw weight to hunt deer. But six years ago, the retired lieutenant colonel found himself an unlikely addition to the gaming community. He’s been the military adviser on all six of the “Call of Duty” games, including “Modern Warfare 2,” which set the record for the highest grossing entertainment launch ever. If the defensive perimeter is set up properly or if the soldiers move and sound as they should, he’s why.