The oslo.context to_policy_values provide the standard arguments that
should be passed to oslo.policy for enforcement. By using these values
heat will automatically gain support for new things like
is_admin_project as they are supported by oslo_context.
Because previously the whole to_dict was passed to policy enforcement we
are actually removing a whole bunch of options that could be used in
policy enforcement - however from a practical perspective i'm not sure
anyone would have used them.
Closes-Bug: #1602081
Change-Id: I244ed767e2077cf43d55104779484b64bd28c85f