The restaurant industry is known for high turnover, but Paul Khoury, the founder and owner of PB&J Restaurants, has come up with an eye-popping incentive for workers: free Harley-Davidsons. “The whole Harley thing came about totally by accident,” said Khoury, who is celebrating 25 years in business. The company’s properties include YaYa’s Euro Bistro, Newport Grill and several Red Robin franchises. Years ago, a new chef named Josh kept quizzing…