Manage `policy.json` file

The default location of this file has been /etc/cinder/policy.json.
Starting Queens release, the default location of this file is changed
to /etc/cinder/policy.yaml.
The policy file to be used may be specified in the /etc/cinder/cinder.conf
file in the [oslo_policy] section as the value of the
`policy_file=policy.json` by default.

Change-Id: I5de35a691c2c3115c13d3db3b220fb8cc4c80355
Related-Prod: PROD-23724 (PROD:23724)
2 files changed