Hanging threads left working when server is shut down

SSHD fails to stop properly due to errant threads. I've attached a thread dump from a point of execution where everything should have been cleaned up. The hanging threads happen only if the server has accepted connections and they do not hang forever, they seem to stop themselves after a minute or so. This might be an executor pool which is not shut down correctly.

Earlier versions (0.8.0 and 0.9.0) did not exhibit this behavior.