in-progress quiz submissions don't fulfill 'must_submit'

test plan:
 - with and without draft state,
  - as a teacher,
   - create and publish a quiz that allows multiple submissions
   - put the quiz in a module
   - set up a "must submit the assignment" requirement
  - as a student,
   - go to the modules page
   - open the quiz in a new tab
   - click "Take the quiz", then don't submit
   - switch back to the browser tab containing the modules page
     and reload
    - the quiz module item should not be complete
   - switch back to the browser tab containing the quiz
     and submit it
   - return to the modules tab and reload
    - the completion requirement should be fulfilled
   - retake the quiz, but do not submit
    - the completion requirement should still be fulfilled

  - as a teacher,
   - create another quiz that allows multiple submissions
   - put the quiz in a module
   - set up a min score requirement
  - as a student,
   - take the quiz and submit, satisfying the min score
     requirement
   - retake the quiz, but do not submit
   - the module item should still be fulfilled

fixes CNVS-6369
fixes CNVS-11567

Change-Id: Iaffe514283f1a51d6ddfb488233e1a12a8a657f9
Reviewed-on: https://gerrit.instructure.com/31460
Tested-by: Jenkins <jenkins@instructure.com>
Reviewed-by: Bracken Mosbacker <bracken@instructure.com>
Product-Review: Bracken Mosbacker <bracken@instructure.com>
QA-Review: Matt Fairbourn <mfairbourn@instructure.com>