fix new admin e-mail notification

fixes CNVS-16348

test plan:
 * add a new admin to an account
 * that person should receive an e-mail notification

Change-Id: I95b90e476f909c425b5585684c87d41ace15380d
Reviewed-on: https://gerrit.instructure.com/43070
Reviewed-by: Rob Orton <rob@instructure.com>
Tested-by: Jenkins <jenkins@instructure.com>
QA-Review: Jeremy Putnam <jeremyp@instructure.com>
Product-Review: Cody Cutrer <cody@instructure.com>