Quiz question integrity after regrade

The problem was that quiz questions were going through some
transformations when generated for a submission, but those
transformations were not applied when we re-generated the questions from
a regrade. This patch makes those xforms happen in both phases.

Closes CNVS-15727

TEST PLAN
---- ----

  - create a quiz with two questions, the second being like MChoice
  - modify the title of the second question
  - take the quiz by a student
  - edit the quiz, and the question, and choose a different answer (and
    make sure it's not what you picked, so you get affected)
    - choose the option to only give full credit to ones who chose the
      *new* answer (again, so the student sub gets affected)
  - reload the student view of the submission and verify:
    - you see the "This question has been regraded." banner
    - you see Question 1 and Question 2 as titles
    - you see the same thing (for titles) from the teacher's perspective

Change-Id: I43a9edc03a381efa0d1c2ccfc7705d0ba912184b
Reviewed-on: https://gerrit.instructure.com/41906
Tested-by: Jenkins <jenkins@instructure.com>
Reviewed-by: Derek DeVries <ddevries@instructure.com>
QA-Review: Trevor deHaan <tdehaan@instructure.com>
Product-Review: Derek DeVries <ddevries@instructure.com>