fix "add login" logout error in rails 3

test plan:
* logged in as an account admin, visit the user page for
 a given user other than yourself
* use the "Add Login" dialog to create a login and
password for the user
* should not log you out and login the edited user

fixes #CNVS-13883

Change-Id: I6104b64dfd9a9557b1f6943bad14e1dcba2168f3
Reviewed-on: https://gerrit.instructure.com/37290
Reviewed-by: Cody Cutrer <cody@instructure.com>
Tested-by: Jenkins <jenkins@instructure.com>
QA-Review: Clare Strong <clare@instructure.com>
Product-Review: James Williams  <jamesw@instructure.com>