This reverts commit 21295bc188.
In a sense, the ans6 black holeserver, based on asyncserver, "does
nothing". In our case, it won't respond to any query, and if the
IgnoreAllConnections connection handler was installed, it would not read
anything from the client socket.
Previously, sending notifications to an unconfigured address resulted in
no communication from the target (10.53.10.53); hence, the ns3
configuration comment requested a "non-responsive notify recipient (no
reply, no ICMP errors)".
However, examining the PCAP of ans6 reveals some communication from the
10.53.0.6 server to the 10.53.0.3 client, including ICMP Destination
Unreachable (Port Unreachable), and TCP SYN/ACK.
The ans6 communication seems to be sufficiently different to touch
different code paths in named, resulting in the BIND 9.20 backport
failing in the "checking notify retries expire within 30 seconds" test.
But we better revert it from "main" as well.
9e7b5a4ad4