docker network prune
`docker network prune` prunes unused networks, including overlay ones. `docker system prune` also prunes unused networks. Signed-off-by: Akihiro Suda <suda.akihiro@lab.ntt.co.jp>
Signed-off-by: allencloud <allen.sun@daocloud.io>
Signed-off-by: Kenfe-Mickael Laventure <mickael.laventure@gmail.com>