Use Tempest-lib's compute hypervisor_client

Compute hypervisor_client has been migrated to
tempest-lib- I1a1dcab8ecd6e12ec03d14303517c8cb1e68ec60

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 hypervisor_client
from Tempest-lib.

Change-Id: I529b3e359250443b2c27b877bf82522102e6a1fb
4 files changed