fix issue with question name count not working for one question at a time

fixes CNVS-12557

test plan:
- as a teacher
  - create a quiz with multiple questions
  - make the quiz a "one question at a time quiz"

- as a student
  - take the quiz
  - questions should use incremental names such as
    "Question 1"
    "Question 2"

- make sure there are no regressions with regrading changing question names
  in /g/32774

Change-Id: Id47f9655853f8344389b5f39a186000008afc602
Reviewed-on: https://gerrit.instructure.com/33770
Tested-by: Jenkins <jenkins@instructure.com>
QA-Review: Caleb Guanzon <cguanzon@instructure.com>
Reviewed-by: Josh Simpson <jsimpson@instructure.com>
Product-Review: Derek DeVries <ddevries@instructure.com>