r/collectd-version: Add OS version plugin

The `collectd-version` script uses the *collectd* UNIX socket to send
custom values to *collectd* to track the OS version.  Since these values
obviously cannot change while the system is running, the values are
specified with a very long interval.  This avoids having to continuously
insert the values, either with a long-running process or by repeatedly
running a script.  The values only need to be inserted once when
*collectd* starts.

roles/collectd-version/handlers/main.yml

@@ -0,0 +1,4 @@
+- name: restart collectd-version
+  service:
+    name: collectd-version
+    state: restarted