cluster/kube: allow system:admin-namespaces to modify ingresses

This will permit any binding to system:admin-namespaces (eg. personal-*
namespaces, per-namespace extra admin access like matrix-0x3c) the
ability to create and updates ingresses.

Change-Id: I522896ebe290fe982d6fe46b7b1d604d22b4f72c

cluster/kube/cluster.libsonnet

@@ -120,6 +120,11 @@ local pki = import "lib/pki.libsonnet";
                     resources: ["jobs", "cronjobs"],
                     verbs: ["*"],
                 },
+                {
+                    apiGroups: ["networking.k8s.io"],
+                    resources: ["ingresses"],
+                    verbs: ["*"],
+                },
             ],
         },
         // This ClusterRoleBindings allows root access to cluster admins.