Use Tempest-lib's compute floating_ip_pools_client

Compute floating_ip_pools_client has been migrated to
tempest-lib- Iab0f7faca8d23d18061c5b3d13bb8b5e0536025c

Now Tempest-lib provides this client as stable interface so Tempest
should start using this from lib and remove its own copy.
Also remove its unit tests.

This commits makes Tempest to use compute floating_ip_pools_client
from Tempest-lib.

Change-Id: I50b5899e80c77fac6c0757b2d1387c49e0cc4e8c
3 files changed