When editing a Openstack compute resource that was already properly associated with an URL and tenant, none of these can be changed.
If you try to change one of these, the moment you click on "Load tenants", it actually performs a "Test connection" on the backend and since it cannot find the old tenant, you can never save it.

```
Unable to save

Expected([200, 204]) <=> Actual(401 Unauthorized) response => #<Excon::Response:0x0000000ada7348 @data={:body=>"{\"error\": {\"message\": \"Could not find project, Personal dlobatog.\", \"code\": 401, \"title\": \"Unauthorized\"}}", :headers=>{"Vary"=>"X-Auth-Token", "Content-Type"=>"application/json", "Content-Length"=>"106", "Date"=>"Sat, 22 Feb 2014 16:09:41 GMT"}, :status=>401, :remote_ip=>"192.168.27.100"}, @body="{\"error\": {\"message\": \"Could not find project, Personal dlobatog.\", \"code\": 401, \"title\": \"Unauthorized\"}}", @headers={"Vary"=>"X-Auth-Token", "Content-Type"=>"application/json", "Content-Length"=>"106", "Date"=>"Sat, 22 Feb 2014 16:09:41 GMT"}, @status=401, @remote_ip="192.168.27.100">
```