Update template to use instance variable

When running on puppet 3.2.3 need to update variable to remove deprecation notice. Not using instance variables targeted for removal in Puppet 4.

Aug 12 08:21:52 puppet puppet-master[18202]: Variable access via 'available' is deprecated. Use '@available' instead. template[inline]:1
Aug 12 08:21:52 puppet puppet-master[18202]:    (at (erb):1:in `block in result')