John Travolta’s ‘Gotti’ had a rocky road to the Cannes Film Festival and the challenges aren’t over yet

The soiree had all the trappings of an ultra-luxe affair: Guests, dressed in tuxedos and evening gowns, wandered the grounds of one of the most expensive hotels in the world, the du Cap-Eden-Roc. Overlooking the Mediterranean Sea, partygoers sipped champagne until 50 Cent — who had been flown in…