Bump nginx-ingress chart to work with kubernetes 1.16

[bacongobbler]

The ingress trait documentation heavily relies on the nginx-ingress chart in the stable repository.

In Kubernetes 1.16, the extensions/v1beta1 API version was dropped for Deployments. Only Deployments with apiVersion: apps/v1 will work.

We should bump the nginx-ingress chart to support Kubernetes 1.16 clusters, as anyone using a more recent version of Kubernetes (e.g. minikube/KinD users) will fall flat in the quickstart.

[bacongobbler]

https://github.com/helm/charts/pull/17343 tries to address this but likely wont be merged.

For the time being, here's what I've changed in the nginx-ingress chart to be compatible with kubernetes 1.16:

in templates/controller-deployment.yaml:

{{- if eq .Values.controller.kind "Deployment" }}
apiVersion: apps/v1
kind: Deployment
metadata:
  labels:
    app: {{ template "nginx-ingress.name" . }}
    chart: {{ .Chart.Name }}-{{ .Chart.Version }}
    component: "{{ .Values.controller.name }}"
    heritage: {{ .Release.Service }}
    release: {{ .Release.Name }}
  name: {{ template "nginx-ingress.controller.fullname" . }}
spec:
  selector:
    matchLabels:
      app: {{ template "nginx-ingress.name" . }}
      component: "{{ .Values.controller.name }}"
      release: {{ .Release.Name }}
      {{- if .Values.controller.podLabels }}
{{ toYaml .Values.controller.podLabels | indent 6 }}
      {{- end }}
  replicas: {{ .Values.controller.replicaCount }}
...

and in templates/default-backend-deployment.yaml:

{{- if .Values.defaultBackend.enabled }}
apiVersion: apps/v1
kind: Deployment
metadata:
  labels:
    app: {{ template "nginx-ingress.name" . }}
    chart: {{ .Chart.Name }}-{{ .Chart.Version }}
    component: "{{ .Values.defaultBackend.name }}"
    heritage: {{ .Release.Service }}
    release: {{ .Release.Name }}
  name: {{ template "nginx-ingress.defaultBackend.fullname" . }}
spec:
  selector:
    matchLabels:
      app: {{ template "nginx-ingress.name" . }}
      component: "{{ .Values.defaultBackend.name }}"
      release: {{ .Release.Name }}
      {{- if .Values.defaultBackend.podLabels }}
{{ toYaml .Values.defaultBackend.podLabels | indent 6 }}
      {{- end }}
  replicas: {{ .Values.defaultBackend.replicaCount }}
...

It's just a matter of submitting those changes as a PR to the nginx-ingress chart.