Fix: add missing RBAC permissions to magnum examples

[GanjMonk]

Similar change was done in #4154

Without these RBAC permissions seeing below in the pod logs:

E1024 14:31:11.976758       1 reflector.go:138] k8s.io/client-go/informers/factory.go:134: Failed to watch *v1.CSIDriver: failed to list *v1.CSIDriver: csidrivers.storage.k8s.io is forbidden: User "system:serviceaccount:kube-system:cluster-autoscaler-account" cannot list resource "csidrivers" in API group "storage.k8s.io" at the cluster scope
E1024 14:31:29.198925       1 reflector.go:138] k8s.io/client-go/informers/factory.go:134: Failed to watch *v1beta1.CSIStorageCapacity: failed to list *v1beta1.CSIStorageCapacity: csistoragecapacities.storage.k8s.io is forbidden: User "system:serviceaccount:kube-system:cluster-autoscaler-account" cannot list resource "csistoragecapacities" in API group "storage.k8s.io" at the cluster scope

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