kubeadm: add instruction to check kubelet status

kubelet can fail to start due to various reason, e.g mismatching cgroup
drivers. Add this step to save user from having to go back and check when
found etcd cluster is not running successfully.

content/en/docs/setup/production-environment/tools/kubeadm/setup-ha-etcd-with-kubeadm.md

@@ -68,6 +68,12 @@ this example.
     systemctl restart kubelet
     ```
 
+    Check the kubelet status to ensure it is running.
+
+    ```sh
+    systemctl status kubelet
+    ```
+
 1. Create configuration files for kubeadm.
 
     Generate one kubeadm configuration file for each host that will have an etcd