As Cyborg is switching to new policy, this is required
to avoid breaking the existing deployment using policy
file in json format and relying on default value of
'CONF.oslo_policy.policy_file'.
Default value of 'CONF.oslo_policy.policy_file' config option
has been changed from 'policy.json' to 'policy.yaml'. If new default
file 'policy.yaml' does not exist but old default 'policy.json' exist
then fallback to use old default file.
An upgrade checks is added to check the policy_file format and
fail upgrade checks if it is JSON formatted.
Added a warning in policy doc about JSON formatted file is deprecated,
also removed all the reference to policy.json file in doc as well as
in tests.
Related Blueprint: https://blueprints.launchpad.net/oslo.policy/+spec/policy-json-to-yaml
Change-Id: I865227e516dc7505c463ac279309169d95ea6a22
af49d0b30a