Background: I use private.py a lot in my devstack for my private configurations. But issues are raised when I need to change/override a setting that is defined in devstack_docker.py file. Since that file's contents are loaded after private.py, my private.py is useless against the settings in devstack_docker.py.
Description: Now that the devstack is dockerized, I think it makes more sense to import the private.py in the devstack_docker.py files i.e. at the end of configuration files hierarchy.
This feature is not well-documented, so it is unclear how to setup Elasticsearch properly to make it work. The next person who needs to work on this feature will need to make it work and, ideally, document it.
