Unpublished quizzes do not show up in student JSON requests

Unpublished quizzes didn't show in JSON-API requests, but this extends
that feature to JSON requests as well.

Fixes CNVS-12272

Test plan:
  - Make two quizzes
  - Publish one
  - Confirm that api/v1/courses/:courseId/quizzes only returns a single
    quiz entry

Change-Id: If5440795d6e29121525425e85dd371f54c38b9e6
Reviewed-on: https://gerrit.instructure.com/38887
Tested-by: Jenkins <jenkins@instructure.com>
Reviewed-by: Ahmad Amireh <ahmad@instructure.com>
QA-Review: Caleb Guanzon <cguanzon@instructure.com>
Product-Review: Ryan Taylor <rtaylor@instructure.com>