* If user doesn't specify the subnets to create a network, it will pick
subnets from inside preferred pool. This PR aims to inspect these subnets info
* Add integration tests for docker inspect the subnets.
* docker-py project is already synchronized.
* jenkins checks depend on https://github.com/docker/docker-py/pull/888
Fixes issue #18626
Signed-off-by: Wen Cheng Ma <wenchma@cn.ibm.com>