workaround to escape variables

passing data from hiera to puppet to configure hiera will replace
variables in your data with their actual values ... there is no way to
escape variables in hiera data. :(

this hack allows to write strings such as v{environment} which will be
written to the template as %{environment}.

see also:
  http://projects.puppetlabs.com/issues/16235
  http://projects.puppetlabs.com/issues/20968