Gather additional facts for haproxy playbook

Our deployment requires extra network interface facts in order
to identify the correct haproxy_stats_bind_address. Adding this
pre-task allows us define filters and gather these without
having to run another playbook or command first.

Change-Id: I2b5ea03d3e65b0d206f57bd48182a96beab793de

playbooks/haproxy-install.yml

@@ -25,6 +25,10 @@
   serial: "{{ haproxy_serial | default('50%') }}"
   user: root
   pre_tasks:
+    - name: Gather additional facts
+      include_tasks: "common-tasks/gather-hardware-facts.yml"
+      tags:
+        - always
     - include_tasks: "common-tasks/os-{{ container_tech | default('lxc') }}-container-setup.yml"
       when: not is_metal
     - include_tasks: common-tasks/unbound-clients.yml