NEW YORK (Reuters) - Television ballroom contest "Dancing With the Stars" took a step back from controversy with its new cast unveiled on Tuesday, including tennis champ Martina Navratilova, several TV actors, an opera singer and Gladys Knight without her "Pips." "Dancing With the Stars" annually is among the top-rated U.S. TV shows with a formula that pairs B-list celebrities, sports stars and singers with professional dancers performing sambas, cha-cha-chas and waltzes across a ballroom floor. ...