corrected breadcrumbs on draft state index

fixes CNVS-11325

test plan:
  - turn draft state on and go to the assignment index
  - click the breadcrumb for assignments
    - it should take you to the same page

Change-Id: I35750202b1e0fe549b12ee9981d947987ce33240
Reviewed-on: https://gerrit.instructure.com/31007
Reviewed-by: Liz Abinante <labinante@instructure.com>
Tested-by: Jenkins <jenkins@instructure.com>
QA-Review: Caleb Guanzon <cguanzon@instructure.com>
Product-Review: Mike Nomitch <mnomitch@instructure.com>