by Vera H-C Chan All that talk about fun is over on " American Idol " and thank goodness for that. The week's theme was R&B, and singer Usher showed up to tell the Top 10 contestants how to "own their moment" on the Fox reality show. Usher, seeking a comeback himself, schooled the wannabe idols on how to claim the stageâ€"just in time. Like every season, a bunch of johnny-come-latelies tune in when the "Idol" touring group has been decided. Right on cue Tuesday night,