Add simple playbook task for upgrading servers

We want to treat our servers as cattle; hopefully when this is fleshed out a bit more, it can accomplish the job without too many casualties.

playbooks/tasks/include/upgrade-server.yml

@@ -37,7 +37,9 @@
 
     - name: abort reboot with logged on users
       meta: end_host
-      when: who.stdout_lines|length > 1
+      when:
+        - who is changed
+        - who.stdout_lines|length > 1
   when: inventory_hostname == "gemini.archlinux.org"
 
 - name: reboot