(maint) Disable shibb testing on redhats

The shibb package is not in the default repos.

Broken in puppetlabs#1657

spec/acceptance/vhost_spec.rb

@@ -1714,7 +1714,7 @@ class { 'apache': }
     end
   end
 
-  describe 'shibboleth parameters' do
+  describe 'shibboleth parameters', :unless => fact('osfamily') == 'RedHat' do
     it 'applies cleanly' do
       pp = <<-EOS
         class { 'apache': }