NBC will finish the 2016-2017 TV season at No. 1 in the key 18-49 demographic group for the third time in four years. The victory mark marks the first time in five years any network has finished on top without the Super Bowl – or even an Olympics. CBS will finish the season as the country’s most-watched network, hanging on to its crown for a ninth consecutive season – and 14 of the last 15 TV seasons. The current TV season doesn’t officially wrap until mid-week, but the…