kubeadm: run kube-proxy on non-master tainted nodes

kube-proxy should be able to run on all nodes, independent
on the taint of such nodes.

This restriction was previously removed in bb28449 but
then was brought back in d194926.

Also, annotate with:
  scheduler.alpha.kubernetes.io/critical-pod: ""

and add a class in the template spec:
  priorityClassName: system-node-critical

cmd/kubeadm/app/phases/addons/proxy/BUILD

@@ -35,7 +35,6 @@ go_library(
     deps = [
         "//cmd/kubeadm/app/apis/kubeadm:go_default_library",
         "//cmd/kubeadm/app/componentconfigs:go_default_library",
-        "//cmd/kubeadm/app/constants:go_default_library",
         "//cmd/kubeadm/app/util:go_default_library",
         "//cmd/kubeadm/app/util/apiclient:go_default_library",
         "//staging/src/k8s.io/api/apps/v1:go_default_library",

cmd/kubeadm/app/phases/addons/proxy/manifests.go

@@ -69,7 +69,10 @@ spec:
     metadata:
       labels:
         k8s-app: kube-proxy
+      annotations:
+        scheduler.alpha.kubernetes.io/critical-pod: ""
     spec:
+      priorityClassName: system-node-critical
       containers:
       - name: kube-proxy
         image: {{ if .ImageOverride }}{{ .ImageOverride }}{{ else }}{{ .ImageRepository }}/kube-proxy-{{ .Arch }}:{{ .Version }}{{ end }}
@@ -104,8 +107,7 @@ spec:
       tolerations:
       - key: CriticalAddonsOnly
         operator: Exists
-      - key: {{ .MasterTaintKey }}
-        effect: NoSchedule
+      - operator: Exists
       nodeSelector:
         beta.kubernetes.io/arch: {{ .Arch }}
 `

cmd/kubeadm/app/phases/addons/proxy/proxy.go

@@ -30,7 +30,6 @@ import (
 	clientsetscheme "k8s.io/client-go/kubernetes/scheme"
 	kubeadmapi "k8s.io/kubernetes/cmd/kubeadm/app/apis/kubeadm"
 	"k8s.io/kubernetes/cmd/kubeadm/app/componentconfigs"
-	kubeadmconstants "k8s.io/kubernetes/cmd/kubeadm/app/constants"
 	kubeadmutil "k8s.io/kubernetes/cmd/kubeadm/app/util"
 	"k8s.io/kubernetes/cmd/kubeadm/app/util/apiclient"
 )
@@ -74,12 +73,11 @@ func EnsureProxyAddon(cfg *kubeadmapi.InitConfiguration, client clientset.Interf
 	if err != nil {
 		return fmt.Errorf("error when parsing kube-proxy configmap template: %v", err)
 	}
-	proxyDaemonSetBytes, err = kubeadmutil.ParseTemplate(KubeProxyDaemonSet19, struct{ ImageRepository, Arch, Version, ImageOverride, MasterTaintKey string }{
+	proxyDaemonSetBytes, err = kubeadmutil.ParseTemplate(KubeProxyDaemonSet19, struct{ ImageRepository, Arch, Version, ImageOverride string }{
 		ImageRepository: cfg.GetControlPlaneImageRepository(),
 		Arch:            runtime.GOARCH,
 		Version:         kubeadmutil.KubernetesVersionToImageTag(cfg.KubernetesVersion),
 		ImageOverride:   cfg.UnifiedControlPlaneImage,
-		MasterTaintKey:  kubeadmconstants.LabelNodeRoleMaster,
 	})
 	if err != nil {
 		return fmt.Errorf("error when parsing kube-proxy daemonset template: %v", err)