Ensure deleted questions aren't returned to API calls

Currently, API calls on lists of questions where some are deleted
return all of the questions.  We want it to only return deleted
questions.

Closes CNVS-12742

Test Plan:
  - Create a quiz with two questions
  - Delete one of the questions
  - Confirm that a visit to /api/v1/courses/1/quizzes/1/questions
    returns a single question

Change-Id: Ic501c6af3b812e4d795fd858012ee8647717789b
Reviewed-on: https://gerrit.instructure.com/38811
Tested-by: Jenkins <jenkins@instructure.com>
Reviewed-by: Derek DeVries <ddevries@instructure.com>
QA-Review: Caleb Guanzon <cguanzon@instructure.com>
Product-Review: Ryan Taylor <rtaylor@instructure.com>