Test: Hold "old ref" while new associated node on same host:port is associated

[ktoso]

Here's what to test:

• Hold "old ref" while new associated node on same host:port is associated
• so the ref refers to some UniqueNode with ID 1111 (example)
• but that node is dead now and another node on the same host:port has replaced it; it has some other ID, like 2222 (example)

Assertions:

• sending messages to that actor ref must yield dead leters -- we know that specific node it was pointing to is dead
• sending messages to that actor ref must not result in receipts on the new node.