‘Arthur’ star will play narrator Lonny in the big-screen adaptation of the rocking Broadway musical. By Jocelyn Vena Russell Brand Photo: Jemal Countess/ Getty Images It seems Russell Brand’s, um, “scheduling” conflicts were cleared up. After the madcap British actor suggested to MTV News in March that he’d be up for a role in the upcoming film adaptation of the hit Broadway musical “Rock of Ages” if salary negotiations went as planned, on Wednesday the movie’s director, Adam Shankman, announced that Brand had been officially cast in the star-filled project. “I can officially announce Russell Brand as your Lonny in #rockofagesmovie!” Shankman wrote on Twitter . “I see a mullet in his future…maybe a Nikki Six?” The part is the latest addition to Brand’s growing r