Install python3-gnocchi in Fedora or RedHat > 7

Fedora repo [1] has python3 packages, start consuming those.

[1] http://trunk.rdoproject.org/fedora/puppet-passed-ci/

Change-Id: I4af4af40749f63ccc4b3294007c204a739b57930

manifests/params.pp

@@ -5,7 +5,8 @@
 class gnocchi::params {
   include ::openstacklib::defaults
 
-  if ($::os_package_type == 'debian') {
+  if ($::os_package_type == 'debian') or ($::os['name'] == 'Fedora') or
+     ($::os['family'] == 'RedHat' and Integer.new($::os['release']['major']) > 7) {
     $pyvers = '3'
   } else {
     $pyvers = ''