dokku should only remove containers created by dokku. It should not remove containers created by others.

I'm running host, with dokku and other docker images. I use 'data-only' container pattern to store data in a 'non-running' container. But dokku removes my non-running data container as well.
http://container42.com/2013/12/16/persistent-volumes-with-docker-container-as-volume-pattern/

https://github.com/progrium/dokku/blob/4aedb6507a3bdec1ff29be2ff60366075186a72e/dokku#L170