Use Tempest-lib's compute fixed_ips_client

Compute fixed_ips_client has been migrated to tempest-lib-
Ic658f09649ed9498fe6d3e7792a7c370772f165b

Now Tempest-lib provides this client as stable interface so Tempest
should start using this from lib and remove its own copy.
Also remove other files for this client like response schema, unit tests.

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

Change-Id: Idce222bc2261e922973ff09878e9c065f5cdf4ec
4 files changed