Two women, strangers to each other, are caught in an airport time warp, waiting for their flights to board. The setup sounds like it could be a nightmare and, at first, it is. “Walter Cronkite is Dead,” directed by Jeannine Grizzard, opened Sunday at the Ashland Contemporary Theatre. Margaret Byers is soft spoken, self-contained and sophisticated. Her tailored gray jacket and silk scarf finish off a stylish look of wealth and privilege.