RM-2260
- fix test failures by removing arbitrary IDs, use UUIDs
- fix more broken tests, replace use of format with %s
- assign uuid to tenant_id
- fix more tests, replace format with %s
- fix pep8 violations
- fix accessing vif_on_device
Merge pull request #45 from jmeridth/fix_updating_of_vif_id_on_device

Stop using vif_id_on_device to find interfaces, just use interface.id