Simplify etcd image version usage in kubeadm

Author: jpbetz

cmd/kubeadm/app/constants/constants.go

@@ -260,11 +260,7 @@ const (
 	MinExternalEtcdVersion = "3.2.18"
 
 	// DefaultEtcdVersion indicates the default etcd version that kubeadm uses
-	DefaultEtcdVersion = "3.3.15"
-
-	// DefaultEtcdImageVersion indicates the etcd image version that kubeadm uses.
-	// For example, the image version of "k8s.gcr.io/etcd:3.3.15-0" is "0".
-	DefaultEtcdImageVersion = "0"
+	DefaultEtcdVersion = "3.3.15-0"
 
 	// PauseVersion indicates the default pause image version for kubeadm
 	PauseVersion = "3.1"

cmd/kubeadm/app/images/images.go

@@ -68,7 +68,7 @@ func GetEtcdImage(cfg *kubeadmapi.ClusterConfiguration) string {
 		etcdImageRepository = cfg.Etcd.Local.ImageRepository
 	}
 	// Etcd uses an imageTag that corresponds to the etcd version matching the Kubernetes version
-	etcdImageTag := fmt.Sprintf("%s-%s", constants.DefaultEtcdVersion, constants.DefaultEtcdImageVersion)
+	etcdImageTag := constants.DefaultEtcdVersion
 	etcdVersion, err := constants.EtcdSupportedVersion(cfg.KubernetesVersion)
 	if err == nil {
 		etcdImageTag = etcdVersion.String()