profile picture should not be clickable if it can't be edited

fixes CNVS-15160

test plan:
 - Create a course with two users enrolled.
 - As one user, go to the other user's /courses/X/users/Y page
 - The profile picture should not be a link and should not be
   clickable.
 - As the same user, go to your own profile page; the profile
   picture should be clickable and let you change your avatar.

Change-Id: I6bac70eef1b23288c5a360058c48742d9a556255
Reviewed-on: https://gerrit.instructure.com/40431
Tested-by: Jenkins <jenkins@instructure.com>
Reviewed-by: Clay Diffrient <cdiffrient@instructure.com>
QA-Review: Clare Strong <clare@instructure.com>
Product-Review: Jon Willesen <jonw@instructure.com>