There were several firsts in Hairspray Live!, NBC’s fourth annual telecast of a Broadway musical (following The Sound Of Music, Peter Pan and last year’s The Wiz!). The hit musical about 1962 Baltimore and one chubby teenage girl’s determination to integrate an American Bandstand-type rock-and-roll TV show brought a live audience after three outings that were marked by dead spots where applause and laughter were wanted — especially in light of Fox’s award-winning Grease!…