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

+---
+
+- name: ensure latest keyring
+  pacman:
+    name: archlinux-keyring
+    state: latest
+    update_cache: yes
+
+- name: upgrade all packages
+  pacman:
+    update_cache: yes
+    upgrade: yes
+  register: pacman_upgrade
+
+- name: reboot
+  reboot:
+  when: pacman_upgrade is changed