Fix Bug 1049964 - Buttons on Email addresses page

Supersedes https://github.com/mozilla/kuma/pull/2728 with new user fixtures and a new test. The original [spot-check instructions](https://github.com/mozilla/kuma/pull/2728#issue-42097490) still apply.
```
jQuery('.action_remove').on('click', function() {
    // ...action stuff
});

```