Ironic enabled secure RBAC with system scoped enforcement [1].

Some API calls, for instance 'baremetal:driver:get' needs system
scope role by design [2], even with elevated access project scope
service role [3].

[1] https://review.opendev.org/c/openstack/ironic/+/902009
[2] https://opendev.org/openstack/ironic/src/commit/8ec56066223301230ac0ed0f0c471a10d366b474/ironic/common/policy.py#L1349-L1357
[3] https://review.opendev.org/c/openstack/kolla-ansible/+/908007

Related-Bug: #2051837

Change-Id: Id6313d7dd343b82d4c9ccf7bf429d340ea0e93d1