If unset reads: - `api_url` from `CLOUDSTACK_API_URL` - `api_key` from `CLOUDSTACK_API_KEY` - `secret_key` from `CLOUDSTACK_SECRET_KEY`
If unset reads: - `api_url` from `CLOUDSTACK_API_URL` - `api_key` from `CLOUDSTACK_API_KEY` - `secret_key` from `CLOUDSTACK_SECRET_KEY`