Add rsyslog module and port existing usage

* Make Puppet manage /etc/rsyslog.d recursively.
* This means that packages that include their own rsyslog.d config will need
  to have that config file declared in Puppet or it will get clobbered on the
  next run.
* This is the same decision we made with respect to sysctl.d.
* Per apt-file, the set of packages with rsyslog.d files are:

   arno-iptables-firewall, cloud-init, gforge-shell-postgresql, maas,
   maas-region-controller, mythtv-common, octopussy, postfix, qpidd, sagan,
   sympa, ubuntu-orchestra-client, ubuntu-orchestra-logging-server, and ufw

  We don't run any of these in production. (We do have ufw installed because
  it's part of the 'standard' tasksel task for Ubuntu, but we don't use it.)
* Remove reference to i-000003a9.pmtpa.wmflabs:5544 as a syslog sink for
  non-beta-cluster hosts; the instance no longer exists.

Change-Id: Ibceb48bd8c475696b900e89f38dea686394069d8