/kind bug

What happened:

when component produces List object, ksonnet unconditionally adds .metadata.labels which doesn't pass validation, because List's .metadata is ListMeta (https://v1-11.docs.kubernetes.io/docs/reference/generated/kubernetes-api/v1.11/#listmeta-v1-meta) , not ObjectMeta

What you expected to happen:

no incorrect modifications being made to Lists objects

How to reproduce it (as minimally and precisely as possible):

make a component which returns List of Lists, example:

{ "apiVersion": "v1",
  "kind": "List",
  "items": [
      {
      "apiVersion": "rbac.authorization.k8s.io/v1",
      "items": [],
      "kind": "RoleBindingList"
      }
  ]
}

Anything else we need to know?:

Environment:

• ksonnet version (use ks version): 0.13
• Kubernetes version (use kubectl version): 1.11