=rem #3527 Throw away system message delivery state when new UID from a remote Address is detected
=rem #3527 Fail fatally when negative acknowledgement is unfulfillable
=rem #3527 Take actor system uid into consideration in remote watch

* When actor system was restarted quickly the new system replied to
  heartbeats and Terminated was never triggered for actors in old
  system.
* Solved by sending an extra Watch system message when first hearbeat
  is received for an address and when a change of system uid is detected.