Failure when inspecting reverse OneToOneFields

``` python
class User(Model):
    meta = OneToOneField(UserMetadata, related_name='user')

class UserMetadata(Model):
    pass
```

When I try to compare UserMetadata instances, I get the following error:

```
Exception Type: AttributeError
Exception Value:    
'User' object has no attribute 'all'
```

It seems that it thinks it is a related manager instead of object.
