* mandos (Client.checked_ok): Set "expires" after setting timeout.
  (MultiprocessingMixIn.process_request): Return process object.
  (MultiprocessingMixInWithPipe.process_request): Receive proc object
                                                  and pass it to
                                                  add_pipe.  Do not
                                                  use super().
  (MultiprocessingMixInWithPipe.add_pipe): Take "proc" argument.  All
                                           callers changed.
  (MandosServer.add_pipe): Take "proc" argument.  All callers changed.
  (MandosServer.handle_ipc): Take "proc" argument.  All callers
                             changed.  Wait for process completion
                             when pipe closes.
  (main/cleanup): Remove any zombies.