WASHINGTON, Sept 2 (Reuters) - The U.S. Federal Aviation Administration (FAA) on Thursday barred Virgin Galactic from flying its SpaceShipTwo until the agency approves its final mishap investigation report from its July flight or determines the issues do not affect public safety. The FAA confirmed on Wednesday it was investigating a deviation in the descent of the flight of the Virgin Galactic rocket plane that carried British billionaire Richard Branson to the edge of space on July 11....