fix: Use kubelet_hostname instead of inventory_hostname_short (#101)

* Use kubelet_hostname instead of inventory_hostname_short

A recent commit introduced further cases of this, originally
fixed in 5c08c72

* Revert hostname change to inventory_hostname_short

roles/kubernetes/tasks/main.yml

@@ -30,7 +30,7 @@
   throttle: 1
   vexxhost.kubernetes.kubeadm_upgrade_node:
     api_endpoint: "https://{{ kubernetes_hostname }}:6443"
-    node: "{{ inventory_hostname_short }}"
+    node: "{{ kubelet_hostname }}"
     version: "{{ kubernetes_version }}"
 
 - name: Set node selector for CoreDNS components