Use subnetpools_client from tempest-lib

The files below have been migrated to tempest-lib

 * subnetpools_client.py: I97b67e2385452db6ef59bc4b8c63c211ca119bc2

Now Tempest-lib provides those as stable interfaces. So Tempest should
start using those from lib and remove its own copy.

Change-Id: Icc34718c0821f2b13ab48aa80e54cd42616d177d
2 files changed