Merge pull request #56015 from luxas/kubeadm_fix_selfhosting_bug

Automatic merge from submit-queue. If you want to cherry-pick this change to another branch, please follow the instructions <a href="https://github.com/kubernetes/community/blob/master/contributors/devel/cherry-picks.md">here</a>.

kubeadm: Fix a small bug in the self-hosting code

**What this PR does / why we need it**:

`apps/v1beta2` requires that `DaemonSet.spec.selector.matchLabels` equals `DaemonSet.spec.template.metadata.labels`. Without this change, the API server rejects the DaemonSet in the validation stage.

**Which issue(s) this PR fixes** *(optional, in `fixes #<issue number>(, fixes #<issue_number>, ...)` format, will close the issue(s) when PR gets merged)*:
Fixes #

**Special notes for your reviewer**:

**Release note**:

```release-note
NONE
```
@kubernetes/sig-cluster-lifecycle-pr-reviews @xiangpengzhao

cmd/kubeadm/app/phases/selfhosting/selfhosting.go

@@ -141,6 +141,9 @@ func BuildDaemonSet(name string, podSpec *v1.PodSpec, mutators map[string][]PodS
 			Labels:    BuildSelfhostedComponentLabels(name),
 		},
 		Spec: apps.DaemonSetSpec{
+			Selector: &metav1.LabelSelector{
+				MatchLabels: BuildSelfhostedComponentLabels(name),
+			},
 			Template: v1.PodTemplateSpec{
 				ObjectMeta: metav1.ObjectMeta{
 					Labels: BuildSelfhostedComponentLabels(name),

cmd/kubeadm/app/phases/selfhosting/selfhosting_test.go

@@ -113,6 +113,9 @@ metadata:
   name: self-hosted-kube-apiserver
   namespace: kube-system
 spec:
+  selector:
+    matchLabels:
+      k8s-app: self-hosted-kube-apiserver
   template:
     metadata:
       creationTimestamp: null
@@ -271,6 +274,9 @@ metadata:
   name: self-hosted-kube-controller-manager
   namespace: kube-system
 spec:
+  selector:
+    matchLabels:
+      k8s-app: self-hosted-kube-controller-manager
   template:
     metadata:
       creationTimestamp: null
@@ -398,6 +404,9 @@ metadata:
   name: self-hosted-kube-scheduler
   namespace: kube-system
 spec:
+  selector:
+    matchLabels:
+      k8s-app: self-hosted-kube-scheduler
   template:
     metadata:
       creationTimestamp: null