For both containers and classic deployments, allow to configure
policy.json for all OpenStack APIs with new parameters (hash,
empty by default).
Example of new parameter: NovaApiPolicies.
See environments/nova-api-policy.yaml for how the feature can be used.
Note: use it with extreme caution.
Partial-implement: blueprint modify-policy-json
Change-Id: I1144f339da3836c3e8c8ae4e5567afc4d1a83e95