add spec to ensure you can change user sis id's with admins_can_change_password=false

refs CNVS-5605

Change-Id: If241724af99c86064a5fc11da44bd58abb171493
Reviewed-on: https://gerrit.instructure.com/40902
Tested-by: Jenkins <jenkins@instructure.com>
Reviewed-by: Nick Cloward <ncloward@instructure.com>
Product-Review: Cody Cutrer <cody@instructure.com>
QA-Review: Cody Cutrer <cody@instructure.com>