As per the community goal of migrating the policy file
the format from JSON to YAML[1], we need to do two things:
1. Change the default value of '[oslo_policy] policy_file''
config option from 'policy.json' to 'policy.yaml' with
upgrade checks.
2. Deprecate the JSON formatted policy file on the project side
via warning in doc and releasenotes.
Also replace policy.json to policy.yaml ref from doc and tests.
CONF object needs to be initialized before policy enforcer(). That
need to remove cfg.CONF.unregister_opts from TestAuthUtils cleanup
as this is taken care by cfg.clear() with proper workflow otherwise
it end up with error
"oslo_config.cfg.ArgsAlreadyParsedError: arguments
already parsed: reset before unregistering options"
- https://b132754ee7062a9ab187-9add4719a9922a9385555a8552fc2366.ssl.cf5.rackcdn.com/768520/5/check/openstack-tox-py38/7964354/testr_results.html
[1]https://governance.openstack.org/tc/goals/selected/wallaby/migrate-policy-format-from-json-to-yaml.html
Change-Id: I1b6c6485bc651fd0b87244a68204036dd4aa37f4