Reload haproxy when static files are changed

If the content of any static files are changed, haproxy must be
reloaded in order for them to be served rather than the previous
versions.

Change-Id: I72101fed2919014bbebbaf4323f72decbea8a638
Signed-off-by: Jonathan Rosser <jonathan.rosser@rd.bbc.co.uk>

tasks/haproxy_pre_install.yml

@@ -91,3 +91,5 @@
     - (item.condition | default(True))
   loop: "{{ haproxy_static_files }}"
   no_log: true
+  notify:
+    - Reload haproxy