Quiz icon in Gradebook doesn't break everything

When the quiz icon shows up and is clicked on to edit, it stalls the JS
on the page, making everything uneditable.  It also doesn't allow for
editing quizzes.

Closes CNVS-16332

Test-plan:
  - Confirm quiz icon edit is functional
  - Confirm other edit fields on the page are still functional

Change-Id: If2d9e5322472ba4bd3474371e5c27b726242ba12
Reviewed-on: https://gerrit.instructure.com/43127
Tested-by: Jenkins <jenkins@instructure.com>
Reviewed-by: Derek DeVries <ddevries@instructure.com>
Reviewed-by: Brian Finney <bfinney@instructure.com>
QA-Review: Trevor deHaan <tdehaan@instructure.com>
Product-Review: Ryan Taylor <rtaylor@instructure.com>