As we are moving to the new S-RBAC policies, we want to use "service"
role for all service to service communication. See [1] for details.
This require from Context class property similar to old "is_advsvc" but
with new naming convention and using new policy rule.
This patch adds this new property together with all required policies
and rules.
For now "ContextBase.is_advsvc" property will return True if one of the
advsvc OR service_role will be True to make it working in the same way
with both old and new policies but once we will get rid of the old
policies we should also remove is_advsvc property from the ContextBase
class.
[1] https://governance.openstack.org/tc/goals/selected/consistent-and-secure-rbac.html#phase-2
Change-Id: Ic401db8b4e2745234e61fe2c05afd5b4ab719a03
8ccdecc7d1