def groom_thread_queues
      still_active = false
      @mutex.synchronize do
        @thread_name_to_queue.delete_if { |_, queue| false == queue.active? }
        still_active = false == @thread_name_to_queue.empty?
      end
      return still_active
    end
def groom_thread_queues
      still_active = false
      @mutex.synchronize do
        @thread_name_to_queue.delete_if { |_, queue| false == queue.active? }
        still_active = false == @thread_name_to_queue.empty?
      end
      return still_active
    end
Deletes any inactive queues from the hash of known queues.

 === Return
 still_active(Boolean):: true if any queues are still active