Revisit aggregate join logic

Not efficient or useful for any other purpose.

      
      #--
      # TODO -- consider is there a better way to optimize this?
      # currently this method is only used by an aggregate join
      def has?(entry) # :nodoc:
        synchronize do
          entry_id = entry.object_id
          
          @rounds.each do |round|
            round.each do |enqued_entry|
              return true if entry_id == enqued_entry.object_id
            end
          end
          false
        end
      end