Chris Willman Music WriterEmbattled country superstar Morgan Wallen returned to public life in a big way during a Luke Bryan concert Friday night, being greeted by a lengthy, roaring standing ovation at Nashville’s Bridgestone Arena as he joined Bryan, Jason Aldean and Tyler Hubbard on stage to do celebratory shots and sing a couple of his greatest hits.It was the second and by far larger of two times Wallen has stepped onto a stage this year since retreating from the limelight in the wake of a