Donald Trump has demanded Joe Biden takes a drug test ahead of the pair’s first head-to-head next month. The 45th President will lock horns with his White House successor in Atlanta on June 27 during CNN’s primetime debate. Trump, who agreed to the two-part televised showdown, shared his thoughts on Biden’s cognitive state and expressed doubts about whether his Democratic rival could take to the stage without additional support. “I just want to debate this guy, but you know, I’m going to demand a drug test, by the way. I am, I really am,” Trump said. He added: “I don’t want him coming in like …