A horse was injured and euthanized Tuesday during production of the racetrack drama "Luck," the third death in connection with the series, and HBO agreed to suspend filming with horses while the accident is investigated. The humane group that oversees Hollywood productions had issued an immediate demand "that all production involving horses shut down." "We are also insisting that this stoppage remain in full effect pending a complete, thorough, and comprehensive investigation," the American Humane...