* replace singletons with provide_charm_instance (in the code and tests)
* select an openstack release based on keystone package due to the lack
of openstack-origin from the principal layer (this is a subordinate, see
https://git.io/vNTyx)
* use reactive triggers to drop config.complete (new configuration
completeness) and config.rendered (non-stale config is rendered) on
config.changed
* do not check config completeness on every event - only when config has
actually changed
* remove the domain configuration file when relation with keystone is
removed (service restart should be performed on the keystone charm side)
* replace path_hash with file_hash (path_hash returns a new dict)
* modify unit tests to reflect the changes
Change-Id: Ied4b6ed64354e3de3c78e6ac809666ee9ae29d1a
Closes-Bug: #1741661
b5fe0ef6c9