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: I9bfa7988174dbbeb26dd7677e28604f6d04fd174

manifests/params.pp

@@ -8,6 +8,10 @@ class magnum::params {
   if ($::os_package_type == 'debian') {
     $pyvers = '3'
     $pyver3 = '3'
+  } elsif ($::os['name'] == 'Fedora') or
+          ($::os['family'] == 'RedHat' and Integer.new($::os['release']['major']) > 7) {
+    $pyvers = '3'
+    $pyver3 = '3.6'
   } else {
     $pyvers = ''
     $pyver3 = '2.7'