Install python3 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: I333042ff90b5fb3eb9270bdaca1f640c3372dcf2

manifests/params.pp

@@ -5,7 +5,8 @@
 class congress::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 = ''