kubeadm: update authored content for 1.12 (reference docs and cluster creation) (#10348)

* kubeadm: update authored content in reference docs for 1.12

* kubeadm: add time frame in create-cluster-kubeadm for 1.12

content/en/docs/reference/setup-tools/kubeadm/kubeadm-init.md

@@ -278,10 +278,11 @@ manager, and scheduler run as [DaemonSet pods](/docs/concepts/workloads/controll
 configured via the Kubernetes API instead of [static pods](/docs/tasks/administer-cluster/static-pod/)
 configured in the kubelet via static files.
 
+To create a self-hosted cluster, pass the flag `--feature-gates=SelfHosting=true` to `kubeadm init`.
+
 {{< caution >}}
-**Caution:** Self-hosting is alpha, but is expected to become the default in
-a future version. To create a self-hosted cluster, pass the `--feature-gates=SelfHosting=true`
-flag to `kubeadm init`.
+**Caution:** `SelfHosting` is an alpha feature. It is deprecated in 1.12
+and will be removed in 1.13.
 {{< /caution >}}
 
 {{< warning >}}
@@ -304,6 +305,11 @@ instead. This requires very careful control over the authentication and
 authorization configuration for your cluster, and may not be appropriate for
 your environment.
 
+{{< caution >}}
+**Caution:** `StoreCertsInSecrets` is an alpha feature. It is deprecated in 1.12
+and will be removed in 1.13.
+{{< /caution >}}
+
 In kubeadm 1.8, the self-hosted portion of the control plane does not include etcd,
 which still runs as a static Pod.