Stop Kazoo when runner stops.
Stop Kazoo when runner stops.

- Otherwise this exposes a Kazoo bug. See <https://github.com/python-zk/kazoo/issues/217>.

EasonYi/incubator-cotton,xujyan/cotton,xujyan/cotton,xujyan/cotton,EasonYi/incubator-cotton,EasonYi/incubator-cotton