I assume you looked at how this is done for compute in trunk.

Approach in trunk is not OK, but sadly I haven't had the time to fix it yet. `connectionCls` is a class and not an instance attribute which means it won't work correctly if you instantiate multiple drivers with a different region.

There are multiple ways to fix and improve this, one way is just using `_ex_connection_class_kwargs`. If we go with this approach we can also move this functionality into `OpenStackDriverMixim` class.