Upload community avatar is shown when only room admin
The upload community avatar form is shown when only room admin.
- We show the avatar upload form if your are a room admin
- But we only accept the avatar if you are a group admin
As discovered when debugging @AlexandreBonneau run-in with this problem, see https://gitter.im/gitterHQ/gitter?at=58dd7c0ddddd87f332d21fba