Use Tempest-lib's compute security_groups_client

Compute security_groups_client has been migrated to
tempest-lib- I4076278b92e8166b52deaa0447047f7dc7a3934a

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 commit makes Tempest to use compute security_groups_client
from Tempest-lib.

Change-Id: I0deeaa2ed353cdd2eeb5f1954fa2bd7c92966e19
4 files changed