allow undelete-ing with draft state enabled

fixes CNVS-11856

test plan
- in a course with draft state enabled
- delete an assignment with submissions
- navigate to /course/:id/undelete
- restore the deleted item
- refresh page; verify item is not listed
- navigate to assignments index; verify item is not listed
- repeat for assignment without submissions

Change-Id: I4e1cf09ad8172de30aea137e69c8c9ed6770041e
Reviewed-on: https://gerrit.instructure.com/32202
Reviewed-by: Simon Williams <simon@instructure.com>
QA-Review: Caleb Guanzon <cguanzon@instructure.com>
Tested-by: Jenkins <jenkins@instructure.com>
Product-Review: Liz Abinante <labinante@instructure.com>