(voxpupuli#77) Enforce unique factsets test

Previosuly the test for unique factsets was created but skipped while the
duplicate files were removed.  Now that the files have been removed, this test
can be enforced.

spec/facts_spec.rb

@@ -18,7 +18,7 @@
   end
 
   describe 'fact files' do
-    xit 'should not contain duplicate fact sets' do
+    it 'should not contain duplicate fact sets' do
       # Gather all of the default files and hash the content
       file_hashes = {}
       FacterDB.default_fact_files.each do |filepath|