Set hostname to health.openneo.net

This doesn't matter-matter, it's just nice for SSH sessions for the
machine to self-report itself as this instead of `localhost`!

setup-machine.yml

@@ -1,9 +1,13 @@
 ---
-- name: Set up user accounts
+- name: Set up host config & user accounts
   hosts: health
   become: yes
   become_user: root
   tasks:
+    - name: Set hostname to health.openneo.net
+      hostname:
+        name: health.openneo.net
+
     - name: Create user account for matchu
       user:
         name: matchu