NEW YORK (AP) — Mark Ballas is returning to Broadway in “Chicago” and the “Dancing with the Stars” pro will be reuniting with an old friend. Ballas, playing slippery lawyer Billy Flynn starting April 6, will share the stage with his Roxie, Whitney Leavitt, the “Secret Lives of Mormon Wives” star who was his dancing partner on “Dancing with the Stars” last year. “I think it’s going to be so fun. We work so well together,” says Ballas, a three-time Mirrorball Trophy winner who has who has done