fix importing of unpublished quiz assignments

test plan:
* import the package referenced in the ticket
* there should be a "Quiz Assignment"
* the link on the wiki front page to the "Quiz Assignment"
 should work

fixes #CNVS-12815

Change-Id: Id4c779da199610783bfd339468532853ebd948bf
Reviewed-on: https://gerrit.instructure.com/34197
Reviewed-by: Jeremy Stanley <jeremy@instructure.com>
Product-Review: Jeremy Stanley <jeremy@instructure.com>
QA-Review: Clare Strong <clare@instructure.com>
Tested-by: Jenkins <jenkins@instructure.com>