Merge pull request #65195 from luxas/kubeadm_fix_cloudprovider_upgrade

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 config upgrading issue with .CloudProvider

**What this PR does / why we need it**:
Fixes a panic in the conversion code where `.NodeRegistration.KubeletExtraArgs` could be nil :/

**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
/kind bug
/priority critical-urgent
/milestone v1.11
/status approved-for-milestone

cmd/kubeadm/app/apis/kubeadm/v1alpha1/conversion.go

@@ -113,6 +113,9 @@ func UpgradeCloudProvider(in *MasterConfiguration, out *kubeadm.MasterConfigurat
 		if out.ControllerManagerExtraArgs == nil {
 			out.ControllerManagerExtraArgs = map[string]string{}
 		}
+		if out.NodeRegistration.KubeletExtraArgs == nil {
+			out.NodeRegistration.KubeletExtraArgs = map[string]string{}
+		}
 
 		out.APIServerExtraArgs["cloud-provider"] = in.CloudProvider
 		out.ControllerManagerExtraArgs["cloud-provider"] = in.CloudProvider