chainloop attestation init returns misleading message if no org exists

If no org exists, we should return a different message than

```
ERR the organization you are trying to access does not exist, please run "chainloop auth login"
```

for example, what we return in other commands

```
you are not part of any organization, please run "chainloop organization create --name ORG_NAME" to create one
``` 

cc/ @jiparis 