ROME — Work on fixed-wing and tiltrotor drones are taking up the slack at an Italian facility run by Leonardo, which has been hit by a slowdown caused by sluggish civil contracts from Boeing, the firm has said.Leonardo had told unions in Rome that the plant at Grottaglie would need to shut down for four months to deal with a decrease in the usual amount of work performed for the 787 Dreamliner passenger.Boeing told its staff in April it expected…