Partially graded quizzes don't show score in gradebook or grade summary

Quizzes which are only partially graded are no longer shown as if they
were fully graded.  Now, the behavior is to show a quiz grading in
progress icon in the gradebook.

Closes CNVS-15073

Test Plan:
  - Create a quiz which contains both autograded and manually graded
    question types (M/C and essay)
  - Take quiz as student
  - Confirm that quiz grades as follows:
    - Student views:
      - Student grade summary view shows quiz icon
    - Teacher view:
      - Teacher gradebook view shows quiz icon

Change-Id: I8261a11f0ffddfb34947ad5f9089aa503b274cb1
Reviewed-on: https://gerrit.instructure.com/40501
Tested-by: Jenkins <jenkins@instructure.com>
QA-Review: Trevor deHaan <tdehaan@instructure.com>
Reviewed-by: Cameron Matheson <cameron@instructure.com>
Product-Review: Hilary Scharton <hilary@instructure.com>