Refactor alert creation to remove unnecessary code

fixes CNVS-12410

test plan:
regression test alert notifications

Change-Id: I3f20a532b0ee39ce2b9e136145f8c7f5f0bc0ba6
Reviewed-on: https://gerrit.instructure.com/33313
Reviewed-by: Cody Cutrer <cody@instructure.com>
Tested-by: Jenkins <jenkins@instructure.com>
QA-Review: Jeremy Putnam <jeremyp@instructure.com>
Product-Review: Simon Williams <simon@instructure.com>