Drop compatibility with very old puppetlabs-inifile

The logic is no longer needed since puppetlabs-inifile 0.10.0[1] and
the current minimum version is 2.0.0.

[1] 2f22483c87

Change-Id: I16bf212137e4b88ca25d026faada88f870c32aea

lib/puppet/provider/ceilometer_config/openstackconfig.rb

@@ -7,7 +7,4 @@ Puppet::Type.type(:ceilometer_config).provide(
     '/etc/ceilometer/ceilometer.conf'
   end
 
-  def file_path
-    self.class.file_path
-  end
 end