Set hostname with a familiar name

This makes it much clearer when you SSH into the machine. I wanted to also changed the host_id to use an underscore, like uk_staging, to match our inventory names. But apparently underscores are not allowed for hostnames. And dashes are not allowed in ansible inventory names.

roles/config/tasks/main.yml

@@ -1,4 +1,8 @@
 ---
+- name: "Set hostname"
+  hostname:
+    name: "{{ host_id }}"
+
 - name: "Set journal log size limit" # to avoid hard drive filling up!
   lineinfile:
     path: /etc/systemd/journald.conf