fix rendering of account groups when you don't have permission to manage them

test plan:
 * create an admin that has read roster permission only
 * as that user, you should be able to go to /accounts/X/groups, and not
   error

Change-Id: I396d99f971cdbd2dd37b8e9a5a5d7ff578fe9667
Reviewed-on: https://gerrit.instructure.com/29009
Reviewed-by: Jacob Fugal <jacob@instructure.com>
Tested-by: Jenkins <jenkins@instructure.com>
QA-Review: August Thornton <august@instructure.com>
Product-Review: Cody Cutrer <cody@instructure.com>