Generate the correct URL for removing role.

Fixes #274 (closed)

Could also fix #266 (closed). Having member object in URL would cause the Casette Mismatch Error as the URL generated would be different than the one existing in the tapes.

Although, I am not sure if #266 (closed) is still a problem. I can't really reproduce it, but as mentioned above, I think that was the reason why it did happen :)