Can not delete organizations

Not sure where `active_packages` is meant to be defined

```
File '/home/adria/dev/pyenvs/ckan_plain/src/ckan/ckan/controllers/group.py', line 458 in delete
  self._action('group_delete')(context, {'id': id})
File '/home/adria/dev/pyenvs/ckan_plain/src/ckan/ckan/logic/__init__.py', line 324 in wrapped
  return _action(context, data_dict, **kw)
File '/home/adria/dev/pyenvs/ckan_plain/src/ckan/ckan/logic/action/delete.py', line 261 in organization_delete
  return _group_or_org_delete(context, data_dict, is_org=True)
File '/home/adria/dev/pyenvs/ckan_plain/src/ckan/ckan/logic/action/delete.py', line 223 in _group_or_org_delete
  for pkg in group.active_packages().all():
AttributeError: 'Group' object has no attribute 'active_packages'
```