scope.lookupvar is slightly more accurate than just using instance variables.
More importantly, this is what was used in many templates. See:
* https://github.com/openshift/puppet-openshift_origin/blob/master/templates/mcollective-client.cfg.erb
* https://github.com/openshift/puppet-openshift_origin/blob/master/templates/node/node.conf.erb
* https://github.com/openshift/puppet-openshift_origin/blob/master/templates/broker/broker_servername.conf.erb