roles/haproxy: Basic setup for HAproxy

The *haproxy* installs HAproxy and sets up basic configuration for it.
It configures the systemd unit to launch the service with the `-f
/etc/haproxy` arguments, which will cause it to load all files from the
`/etc/haproxy` directory, instead of just `/etc/haproxy/haproxy.cfg`.
This will allow other roles to add frontend and backend configuration by
adding additional files to this directory.

roles/haproxy/handlers/main.yml

@@ -0,0 +1,10 @@
+- name: reload systemd
+  command: systemctl daemon-reload
+- name: restart haproxy
+  service:
+    name=haproxy
+    state=restarted
+- name: reload haproxy
+  service:
+    name=haproxy
+    state=reloaded