corrected the preview message for a quiz with all changes published

when previewing a quiz, the preview message now correctly displays
whether the quiz is a draft or published.

fixes CNVS-13984

test plan:
- Create a quiz in a course with at least one question in it.
- Publish the quiz.
- Click on the gear icon in the top right corner of the quiz description page and click "Preview".
- Notice the message correctly displays "This is a preview of the published version of the quiz".
- Unpublish the quiz.
- Click on the "Preview" button in the top right corner of the quiz description page.
- Notice the message correctly displays "This is a preview of the draft version of the quiz".

Change-Id: Ia3db9b602f927a2d04098987bdd7174a71114bf1
Reviewed-on: https://gerrit.instructure.com/41838
Reviewed-by: Josh Simpson <jsimpson@instructure.com>
Tested-by: Jenkins <jenkins@instructure.com>
QA-Review: Trevor deHaan <tdehaan@instructure.com>
Product-Review: Spencer Olson <solson@instructure.com>