Bugfixes and refactoring

I couldn't get your cookbook to work on my RHEL6 system. These fixes not only make it work, but add additional functionality:

* Fix node attribute formatting for FC001 compliance (even though that Foodcritic rule was turned off, most people seem to have gravitated towards strings)
* Enable iptables rule for Spacewalk
* On EC2, many images do not have enough space on their root volume to host /var/lib/pgsql, so I used Rightscale's ephemeral_lvm cookbook to automatically stand up an /mnt/ephemeral to hold the data, otherwise the spacewalk-setup-postgresql will fail.