Merge pull request #43161 from luxas/kubeadm_16_offline_version

Automatic merge from submit-queue

kubeadm: Default to v1.6.0 stable in offline scenarios in beforehand

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

In offline scenarios, kubeadm will fallback to the latest well-known version.
This PR bumps that to v1.6. We can merge now, and in the small gap between the merge of this PR and the actual v1.6 release, kubeadm devs will have to explicitely set k8s version.

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

**Special notes for your reviewer**:

**Release note**:

```release-note
NONE
```
@jbeda

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

@@ -28,7 +28,7 @@ const (
 	DefaultServicesSubnet    = "10.96.0.0/12"
 	DefaultKubernetesVersion = "latest-1.6"
 	// This is only for clusters without internet, were the latest stable version can't be determined
-	DefaultKubernetesFallbackVersion = "v1.6.0-beta.1"
+	DefaultKubernetesFallbackVersion = "v1.6.0"
 	DefaultAPIBindPort               = 6443
 	DefaultDiscoveryBindPort         = 9898
 	DefaultAuthorizationMode         = "RBAC"
@@ -46,7 +46,7 @@ func addDefaultingFuncs(scheme *runtime.Scheme) error {
 
 func SetDefaults_MasterConfiguration(obj *MasterConfiguration) {
 	if obj.KubernetesVersion == "" {
-		obj.KubernetesVersion = DefaultKubernetesVersion
+		obj.KubernetesVersion = DefaultKubernetesFallbackVersion
 	}
 
 	if obj.API.BindPort == 0 {

cmd/kubeadm/app/cmd/cmd.go

@@ -56,7 +56,7 @@ func NewKubeadmCommand(f cmdutil.Factory, in io.Reader, out, err io.Writer) *cob
 			    ┌──────────────────────────────────────────────────────────┐
 			    │ On the second machine                                    │
 			    ├──────────────────────────────────────────────────────────┤
-			    │ node# kubeadm join --token=<token> <ip-of-master>        │
+			    │ node# kubeadm join --token=<token> <ip-of-master>:<port> │
 			    └──────────────────────────────────────────────────────────┘
 
 			    You can then repeat the second step on as many other machines as you like.

cmd/kubeadm/app/constants/constants.go

@@ -57,7 +57,7 @@ const (
 	SchedulerKubeConfigFileName         = "scheduler.conf"
 
 	// Important: a "v"-prefix shouldn't exist here; semver doesn't allow that
-	MinimumControlPlaneVersion = "1.6.0-beta.1"
+	MinimumControlPlaneVersion = "1.6.0-beta.3"
 
 	// Some well-known users and groups in the core Kubernetes authorization system