Apache vhost is now the default frontend plugin
Ensure we don't attempt to change the node frontend

We want to ensure that the only time we change the node frontend is
on first puppet run. So create a marker file[1] via exec, create a file
based on an inline template that will update whenever there are changes
to the node_frontend_plugins. Diff those two before altering node.conf
or installing node plugins.
Before writing markers require rubygem-openshift-origin-node
Merge pull request #310 from sdodson/vhost-default

Apache vhost is now the default frontend plugin. Ensure that puppet, after first run, doesn't attempt to change node frontends as it requires manual intervention.