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/tasks/main.yml

@@ -0,0 +1,43 @@
+- name: ensure haproxy is installed
+  package:
+    name=haproxy
+    state=present
+  tags:
+  - install
+
+- name: ensure haproxy unit configuration extension directory exists
+  file:
+    path=/etc/systemd/system/haproxy.service.d
+    mode=0755
+    state=directory
+- name: ensure haproxy config variable override is set
+  copy:
+    src=haproxy-config.conf
+    dest=/etc/systemd/system/haproxy.service.d/config.conf
+    mode=0644
+  notify:
+  - reload systemd
+  - restart haproxy
+- name: ensure default haproxy configuration file is empty
+  copy:
+    src=haproxy.cfg
+    dest=/etc/haproxy
+    mode=0644
+  notify: restart haproxy
+- name: ensure haproxy global configuration is set
+  template:
+    src=global.cfg.j2
+    dest=/etc/haproxy/10-global.cfg
+    mode=0644
+  notify: restart haproxy
+- name: ensure haproxy defaults are set
+  template:
+    src=defaults.cfg.j2
+    dest=/etc/haproxy/20-defaults.cfg
+    mode=0644
+  notify: restart haproxy
+
+- name: ensure haproxy starts at boot
+  service:
+    name=haproxy
+    enabled=yes