In Alexander Ullom’s unpredictable horror film “It Ends,” four friends driving home from college realize that they’re on an endless road. (Neon) By NICOLAS RAPOLD The open road has a grand tradition in American movies. You hit the highway, meet people along the way, see some sights and get where you’re going with a fresh perspective. The future is yours. This is not how “It Ends” works. In Alexander Ullom’s unpredictable horror film, four friends driving home from college realize that they’re…