Fixed issue with sync_schemas not recognising models in directory

The hasattr test was giving me problems with an app (Zinnia blog) which splits out its models into submodules - testing for the 'models' attribute on the models module fails in this instance, meaning the schemas don't get fully synced when a new tenant is set up.

I'm not sure what the original purpose of the test was but as far as I can tell get_apps() and get_models() appear to be sufficient to identify the models.