R. Kelly’s new album Double Up (May 29) is chock-full of collabos. He’s got everyone from T.I. and Chamillionaire to Usher and Kid Rock on there. This particular song is called “Best Friend” and features Keyshia Cole and producer Polow Da Don. The song includes the most ridiculous R. Kelly line ever: “This toilet paper be cuttin’ my ass, I need some rolls of tissue, Charmin, and man what happened to the squares your ass promised me?” Only Kels…