Race in creating new remote child, see #3423

* RemoteSystemDaemon removes its child when sendSystemMessage
  DeathWatchNotification is called from tellWatchersWeDied.
  That can happen after Terminated is delivered to other watcher,
  which create a new child with same name, and then the new child
  can then be removed instead of the old one.
* RemoteSystemDaemon must only remove child with exact match of
  full ActorRef