Print test method names as we run them

Sometimes the DefaultDockerClientTest class can take a while to run all its
tests. This gives us some indication into progress, and lets us (and the
build system) check that the build hasn't just stalled.
Oh, we don't include any logging libraries, so nothing can be logged during the tests anyway. Maybe remove the `log` variable since it's unused, and wouldn't work anyway? Printing to systemout is probably good enough for now, but we might want to setup logging for the tests at some point.