(portage-#25) Don't modify persistent hash contents

The previous implementation of PortageFile.build_line was modifying the
hash representation of a record when constructing lines, so each
successive write of the record would modify it more.

This would only affect package_use and package_keywords since they would
need to modify the record line while the portage_mask and portage_unmask
would directly write :name to disk.

lib/puppet/util/portage.rb

@@ -94,7 +94,7 @@ def format_atom(hash)
       str << '-'
       str << ver_hash[:version]
     else
-      str = hash[:name]
+      str = hash[:name].dup
     end
 
     str