No one could blame you if upon hearing the title of “An Inspector Calls,” the current play at Chicago Shakespeare’s Yard Theater, you thought it would be a British mystery whodunit in the tradition of Agatha Christie.But you would be wrong. It is a mystery and there is a death involved, but it is a suicide, not a murder. And there is an inspector (of sorts) in a very acerbic portrayal by Liam Brennan who …