The original design of k8s cluster health status is allowing
the health status being updated by Magnum control plane. However,
it doesn't work when the cluster is private. This patch supports
updating the k8s cluster health status via the Magnum cluster
update API by a 3rd party service so that a controller (e.g.
magnum-auto-healer) running inside the k8s cluster can call
the Magnum update API to update the cluster health status.
Task: 38583
Story: 2007242
Change-Id: Ie7189d328c4038403576b0324e7b0e8a9b305a5e
63e80c3108