cinder policy file location changed

[Adam Vinsh]

From: https://docs.openstack.org/cinder/latest/configuration/block-storage/samples/policy.yaml.html
From queens the cinder policy file location has changed to "policy.yaml"

Right now in an os_cinder rocky install for example, the policy.json file is ignored.

One must set:
The default policy file location is /etc/cinder/policy.yaml. You may override this by specifying a different file location as the value of the policy_file configuration option in the [oslo_policy] section of the the Cinder configuration file.

So for os_cinder role we need
 - to add an oslo_policy section for the cinder.conf template
 - Document that prior to queens it was "policy.json" but starting in queens it is "policy.yaml" unless you specifically override it.

[Dmitriy Rabotyagov (noonedeadpunk)]

This has been originally covered with https://review.opendev.org/#/c/665499. However, until now we didn't cherry-pick it to the previous branches. I've just cherry-picked this change up to the queens release.

[Dmitriy Rabotyagov (noonedeadpunk)]

Also, eventually, you can add this section with cinder_cinder_conf_overrides in the previous releases, util patches land

[Adam Vinsh (adam-vinsh)]

Got it, thank you for the patch.