fix tests: use of .once means no events left over after stickit:unstuck called
fix tests: use of .once means no events left over after stickit:unstuck called

akre54/backbone.stickit,Krasnyanskiy/backbone.stickit,Krasnyanskiy/backbone.stickit,adam-26/backbone.stickit,NYTimes/backbone.stickit,akre54/backbone.stickit,adam-26/backbone.stickit,NYTimes/backbone.stickit