Show Quiz icon in module items

Fixes CNVS-10921

Test plan:

  - create a quiz and create a module that includes it
  - refresh the modules page
  - verify that the quiz item shows the quiz icon (Q) and not the blank
    document one

Change-Id: Icea7fa4b02a478e0c1a459339513e02a7f5d8fdb
Reviewed-on: https://gerrit.instructure.com/29564
Tested-by: Jenkins <jenkins@instructure.com>
Reviewed-by: Jason Madsen <jmadsen@instructure.com>
QA-Review: Caleb Guanzon <cguanzon@instructure.com>
Product-Review: Ahmad Amireh <ahmad@instructure.com>