v1.6.31 - Stopping the container stops the server

docker stop never reached the server: the container sat out Docker's grace period and was then
killed. It now shuts down in a second or two. A server that stops also hands its cache folder back,
so after an upgrade or a recreated container the new one cleans the cache straight away, instead of
logging "claimed by another server" and waiting five minutes.

Upgrade: pull it.