Update Ingress apiVersion before kube v1.18

[jjo]

Kubernetes v1.18 fully deprecates Ingress resource apiVersion extensions/v1beta1, need to use networking.k8s.io/v1beta1 which is available since v1.14.

We should fix it before beta, v1.18.0-alpha.1 has just been released, excerpt from https://github.com/kubernetes/kubernetes/blob/master/CHANGELOG-1.18.md#other-notable-changes

• kube-apiserver no longer serves the following deprecated APIs: (#85903, @liggitt)
  • [n/a] All resources under apps/v1beta1 and apps/v1beta2 - use apps/v1 instead
  • [x] daemonsets, deployments, replicasets resources under extensions/v1beta1 - use apps/v1 instead [#23]
  • [x] networkpolicies resources under extensions/v1beta1 - use networking.k8s.io/v1 instead [#34]
  • [x] podsecuritypolicies resources under extensions/v1beta1 - use policy/v1beta1 instead [#23]