KNOXVILLE — North Carolina’s men’s basketball team passed the kind of road challenge it wanted to face before starting Atlantic Coast Conference competition. Kenny Williams sank a go-ahead 3-pointer with 35 seconds left and the seventh-ranked Tar Heels rallied past No. 20 Tennessee 78-73 on Sunday. This was the first game North Carolina (10-1) played all season that was decided by a single-digit margin.