Cher and her son Elijah Blue Allman’s conservatorship battle will continue to drag out. Legal documents obtained by RadarOnline.com show the legendary singer, 77, and her 47-year-old son’s day in court has been postponed to September 13. Cher’s legal fight to take control of Elijah’s life and finances was on the books for June 11. RadarOnline.com told you first — the pair agreed to pump the brakes on their nasty conservatorship feud after Elijah, whom she welcomed with her late ex-husband Gregg Allman, demanded the court deny his famous mom’s request for his medical records. On May 7, Cher and…