maxDelay bounds the wait and sets the bar a link must clear, and only the
first was documented, so tuning it up quietly lengthened every recovery.
The unreadable PDU the tests write is one named constant now.
A bind that returns is not proof the link works: an unreadable stream is
only found afterwards, so resetting the delay there handed a link that
died on arrival a fresh minDelay every cycle — one connect and bind per
second forever, which is how an account gets blocked for bind flooding.
The loop resets only once a link has outlasted maxDelay.
Also covers the unreadable stream that has no loop to retry it.
`close` fires only where nothing will bring the session back; a drop the
reconnect loop will retry is `disconnected`, pairing with `reconnected`.
`minDelay: 0` never doubles, so the backoff never started — both delays
are range-checked now, and only `false` spells reconnect off.
lilleman