Merge pull request #63684 from timothysc/priority

Automatic merge from submit-queue (batch tested with PRs 63673, 63712, 63691, 63684). 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>.

Add 'system-cluster-critical' to kubeadm control plane pods.

**What this PR does / why we need it**:
Add 'system-cluster-critical' to kubeadm control plane pods.

**Which issue(s) this PR fixes**:
Fixes https://github.com/kubernetes/kubeadm/issues/395

**Special notes for your reviewer**:

**Release note**:

```
NONE
```

/cc @kubernetes/sig-cluster-lifecycle-pr-reviews

cmd/kubeadm/app/util/staticpod/utils.go

@@ -64,9 +64,10 @@ func ComponentPod(container v1.Container, volumes map[string]v1.Volume) v1.Pod {
 			Labels: map[string]string{"component": container.Name, "tier": "control-plane"},
 		},
 		Spec: v1.PodSpec{
-			Containers:  []v1.Container{container},
-			HostNetwork: true,
-			Volumes:     VolumeMapToSlice(volumes),
+			Containers:        []v1.Container{container},
+			PriorityClassName: "system-cluster-critical",
+			HostNetwork:       true,
+			Volumes:           VolumeMapToSlice(volumes),
 		},
 	}
 }

cmd/kubeadm/app/util/staticpod/utils_test.go

@@ -286,8 +286,9 @@ func TestComponentPod(t *testing.T) {
 							Name: "foo",
 						},
 					},
-					HostNetwork: true,
-					Volumes:     []v1.Volume{},
+					PriorityClassName: "system-cluster-critical",
+					HostNetwork:       true,
+					Volumes:           []v1.Volume{},
 				},
 			},
 		},