Before this change we had a race condition bug: if stderr was closed
before the other two sockets, we wouldn't properly detect when the
server died, and not report or retry anything.
That's because we treated a closed stderr as a non-error.
Technically, it isn't an error (closing a connection is okay!), but
until we have a proper shutdown ceremony between all three processes, we
can treat it as an error, because that lets us to detect when the server
is gone.
On the client-side, we also always react to these errors by
reconnecting. Except when we shutdown: there we do a proper shutdown and
won't error on the proxy exit code.
So, this works, even if I wish there was a better way for the server to
communicate to the proxy that it shutdown properly. But I don't want a
fourth socket.
Release Notes:
- N/A
69abe71bf7