R. Kelly has been returned to the federal jail in downtown Chicago ahead of his trial on child pornography and obstruction-of-justice charges, just two weeks after the disgraced R&B star was sentenced in New York to 30 years in prison for racketeering and sex trafficking.The 55-year-old Kelly was transferred Tuesday from the federal jail in Brooklyn to the Metropolitan Correctional Center, the Chicago Tribune reported. He was also held at the Chicago lockup after he was indicted on federal charges in Chicago and New …