Fix method references:

Historically, all of the variables visible in the current scope were also available as Ruby methods
— that is, fqdn, memoryfree, operatingsystem, etc., without the prepended @ sign. This style of
reference caused problems when variable names collided with Ruby method names; its use emits
deprecation warnings as of Puppet 3 and will be removed in Puppet 4. Please update any existing
code which uses it and start any new code out with the @fqdn instance-variable syntax.
http://docs.puppetlabs.com/guides/templating.html#referencing-variables