markFailed
fun markFailed(nowEpochSecs: Long, backoffRatio: Int = TrackerBackoff.DEFAULT_BACKOFF_RATIO, retryIntervalSecs: Int = 0)
Record a failed announce at nowEpochSecs, porting announce_infohash::failed: bump fails (saturating at 127), mark not-working, and push nextAnnounceEpochSecs out by the exponential back-off in TrackerBackoff.nextDelaySecs. retryIntervalSecs is libtorrent's retry_interval floor (e.g. a tracker-supplied retry hint).