Merge pull request #65764 from rosti/fix-65757

Automatic merge from submit-queue (batch tested with PRs 65719, 65764). 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 CoreDNS image generation bug

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

With #64976 GetGenericArchImage was used for generating the CoreDNS image path.

This generated incorrect image in the form `prefix/coredns-goarch:tag` instead
of just `prefix/coredns:tag`.

Signed-off-by: Rostislav M. Georgiev <rostislavg@vmware.com>

**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 #65757

**Special notes for your reviewer**: 
/cc @kubernetes/sig-cluster-lifecycle-pr-reviews
/area kubeadm
/assign @luxas
/assign @timothysc
/kind bug

**Release note**:

```release-note
NONE
```

cmd/kubeadm/app/images/images.go

@@ -77,7 +77,7 @@ func GetAllImages(cfg *kubeadmapi.MasterConfiguration) []string {
 
 	dnsImage := GetGenericArchImage(cfg.ImageRepository, "k8s-dns-kube-dns", constants.KubeDNSVersion)
 	if features.Enabled(cfg.FeatureGates, features.CoreDNS) {
-		dnsImage = GetGenericArchImage(cfg.ImageRepository, "coredns", constants.CoreDNSVersion)
+		dnsImage = fmt.Sprintf("%s/%s:%s", cfg.ImageRepository, constants.CoreDNS, constants.CoreDNSVersion)
 	}
 	imgs = append(imgs, dnsImage)
 	return imgs