fix 'everyone' tab link

test plan:
* add a group to a course
* visit the 'People' page
* cliking on the 'Everyone' tab should not take you to
/courses/1/users

refs #CNVS-14011

Change-Id: Icc8d662d6165b6f746c623fa24e867f44c6a536c
Reviewed-on: https://gerrit.instructure.com/37488
Tested-by: Jenkins <jenkins@instructure.com>
Reviewed-by: Matthew Wheeler <mwheeler@instructure.com>
QA-Review: Clare Strong <clare@instructure.com>
Product-Review: James Williams  <jamesw@instructure.com>