Update for usability and liberty nova API change
Update for usability and liberty nova API change

  - Fix Nova API v2.1 broke creating servers
  - Ensure onlly max_instances_per_tenant are created
  - Ensure at least one network will be created

Change-Id: I47c0c74635bcea25c80bcb2f76543c63d9471b8e

cisco-openstack/tempest,cisco-openstack/tempest