Dolly Parton is not a rock singer.Nor — as her much-hyped head-banger makeover on “Rockstar” demonstrates — does she have any business making a “rock” album.But, at 77, the country legend has, as much as any living artist today, more than earned the right — at least three lifetimes over — to do whatever the hell she wants.And really, this whole vanity project was fueled by the humility with which Parton has become a goddess on earth. After she was nominated for the Rock & Roll of Fame last year, she gracefully and ever-so-graciously asked for her name to be withdrawn from the ballot.“I don’t feel that I have earned that right,” she said in a statement.