Don't remove course update when clicking outside modal.

Fixes bug STUD-822.

@dmitchell Please review. The acceptance test that failed is unrelated to the change (I reported it to Will).

Note that the bug fix is the one-word change to pass false to closeEditor instead of self. I had to change how the modalCover variable was defined so that I could unit test the bug fix. When I first wrote the tests, they were trivially passing in the "click outside of modal" case because that wasn't actually closing the dialog (variable was undefined when the test ran). I added the spy checks to show and hide to make sure the modalCover is really being used.