After a secret was created, when we add the cluster to the clusterStore, we should also add the cluster to the same pilot as istio control plane.

But for now, we only add cluster to the istio control plane pilot when the clusterStore was initiated before deploy the istio control plane. This will cause the dynamic created secrets will not add its cluster to the istio control plane pilot.

I think the fix is we should add such logic https://github.com/istio/istio/blob/release-0.8/pilot/pkg/bootstrap/server.go#L530-L554 to secretController addMemberCluster.

And we should also delete the cluster from istio control plane pilot when delete the secret.

/cc @sdake @sbezverk