Saving the forum settings form when the activity has grades disables grading

Master:

1. Login as teacher
2. Create a forum:
   1. Set Whole forum grading to Point-based
   2. Set up some form of ratings (anything will do)
   3. Save
3. Edit the forum settings
4. Expand the "Grade" section
   1. Confirm that the "Rating" settings are visible and not disabled
   2. Confirm that the "Whole forum grading" settings are visible and not disabled
5. Login in a second browser as a student
6. Create a discussion in the forum
7. Close the student window and go back to being a teacher again
8. View the discussion and give a Rating for the post
9. View the list of discussions
10. Click on the "Grade users" button
11. Give the user a grade
12. Edit the forum settings
13. Expand the "Grade" section
    1. Confirm that the "Rating" settings are visible but disabled
    2. Confirm that the "Whole forum grading" settings are visible but disabled
14. Save changes on the page
15. Edit the forum settings again
16. Expand the "Grade" section
    1. Confirm that the "Rating" settings are visible but disabled
    2. Confirm that the "Whole forum grading" settings are visible but disabled

All branches (including master):

1. Create an assignment
2. Edit settings for the assignment
3. Expand the "Grade" section
   1. Confirm that the grade settings are visible and not disabled
4. As a teacher grade any student (you don't need to upload content for that student)
5. Edit settings for the assignment
6. Expand the "Grade" section
   1. Confirm that the grade settings are visible but disabled
7. Save changes
8. Edit settings for the assignment again
9. Expand the "Grade" section
   1. Confirm that the grade settings are visible but disabled