Are there any real hip-hop stars left without a vodka brand? “Saturday Night Live” star Andy Samberg and his Lonely Island posse have signed as “creative directors” of Diageo’s Rokk Vodka. New Yorkers who’ve noticed ads for Lonely Island’s latest album, “Turtleneck and Chain,” may have thought Rokk was a joke since the beverage appears in campaigns for the comedy album. But guests at a UTA and United Entertainment Group upfront bash Sunday at Lavo learned the Swedish booze is for real when they found the venue stocked with the stuff. “Turtleneck and Chain” features Akon and Rihanna for added street cred.