It’s reassuring to know celebrities get snarled up in the UN traffic as well as mere mortals. An insider reports actor Clive Owen “was an hour late to dinner” to the Bon Appetit Supper Club and Café, at Sixth Avenue and 57th Street, Wednesday night, when police had most Upper East Side cross streets blocked off. Owen was celebrating the premiere of his new movie, “The Boys Are Back,” with a dinner by Emeril Lagasse.