Use Tempest-lib's compute instance_usage_audit_logs

Compute instance_usage_audit_logs has been migrated to
tempest-lib- I3c104b49903e5762041c370e3e9803a382de76fa

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 instance_usage_audit_logs
from Tempest-lib.

Change-Id: I2f1e1c0500eb1f52a3fe64031d79f01b9bd57dc2
4 files changed