test/smoke: nuke docker registry before all tests
test/smoke: nuke docker registry before all tests

- Without this, tests for artifact operations are not isolated
  between test runs. Up to now that has not mattered so much.
- Also parallelises long smoke test startup tasks, makes a big
  difference when iterating on a single test...

opentable/sous,samsalisbury/sous,opentable/sous,samsalisbury/sous,opentable/sous,samsalisbury/sous,opentable/sous,samsalisbury/sous,samsalisbury/sous,opentable/sous