Use interfaces_client from tempest-lib

The files below have been migrated to tempest-lib

 * interfaces_client.py: I758cf64ba1e6f760a60ed253cb9a8c9bc75ba73b
 * interfaces.py: I758cf64ba1e6f760a60ed253cb9a8c9bc75ba73b
 * test_interfaces_client.py: I758cf64ba1e6f760a60ed253cb9a8c9bc75ba73b

Now Tempest-lib provides those as stable interfaces. So Tempest should
start using those from lib and remove its own copy.

Change-Id: I0d488b89f4f75df55fb7490771d7cb8766ec275e
5 files changed