1. Users requests to join a language team
2. An admin adds user to language team directly (not via requests page)
3. Another admin goes to the requests page and accepts the join request
No requests visible, or "Note: this user is already in the team"
Request appears to be accepted. Clicking "accept" presumably doesn't change any language permissions.
If someone fulfils a request manually, Zanata should dismiss the request, whether the permission change was done through the requests system or not. Or failing that, the requests system should show a warning when viewing the request.