NEW YORK — If Neil Patrick Harris had his way, Britney Spears would be banned from the set of "How I Met Your Mother." Nothing against the pop singer personally _ he just doesn't think the show should bring guests aboard for a ratings boost alone. "I'm in the minority that our show does not need stunt casting in order to succeed," Harris declared during a break from taping the Monday night CBS sitcom, which has grown a cult following since its 2005 debut. "I worry that if they ...