Install Kubernetes 1.11 and go back to Ubuntu Xenial until Bionic is officially supported

roles/kubernetes/tasks/kubeadm-token.yml

@@ -0,0 +1,26 @@
+---
+- block:
+    - name: Get an existing kubeadm join token
+      shell: |
+        kubeadm token list 2>/dev/null \
+          | awk '$4 == "authentication,signing" { print $1 }' \
+          | head -n1
+      register: kubeadm_token_list
+      changed_when: False
+      check_mode: False
+      failed_when: False
+
+    - name: Generate a new kubeadm token
+      shell: "kubeadm token create 2>/dev/null || kubeadm token generate"
+      register: kubeadm_token_create
+      when: kubeadm_token_list.stdout | length == 0
+
+    - set_fact:
+        kubeadm_token: |-
+          {%- if kubeadm_token_list.stdout | length > 0 -%}
+            {{ kubeadm_token_list.stdout }}
+          {%- else -%}
+            {{ kubeadm_token_create.stdout }}
+          {%- endif -%}
+
+  when: kubeadm_token|default('') | length == 0