Kasey Kahne, by his own admission, is NASCAR’s version of “Mr. Clean.” What else can you say after Bristol’s big fireworks show that never exploded? He had several prized opportunities Saturday to turn Matt Kenseth’s Dollar General Toyota and skate by for the win and a season sweep at the half-mile track. No one would have blamed him, either. All season, the No. 5 car has been swung into SAFER Barriers like clockwork by Kenseth and his teammates; they’ve made the old Allstate cougar accidents seem minor by comparison.