Ben Affleck likes to play poker, but it was all work for the actor Monday at the Mohegan Sun. Affleck and his co-stars in “The Town” — Blake Lively, Jon Hamm, Chris Cooper and Jeremy Renner — took a road trip from Boston to Uncasville, Conn., to shoot a scene in the casino. From a dawn casting call, more than 100 extras were selected as background gamblers. The movie — based on the book “Prince of Thieves” by Chuck Hogan — features Affleck as a robber in love with a bank manager who was one of his victims.