chore(registry): bump version to v0.8.1
test(registry): remove unit tests

the unit tests are outdated, useless and consistently failing. We were
cloning and running the unit tests correctly some months ago, but now
it requires a local redis. Unit tests are covered by
docker/docker-registry, anyways.
refactor(scheduler): switch to fleet http api
chore(*): bump CoreOS to 438.0.0; Docker to 1.2.0; fleet to 0.8.0
hack(tests): query router to remove stale nginx worker
fix(tests): remove fragile docker inspect, sleep 5s on every curl