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.
I don't know. The thing with log is that these are really INFO-level messages. But I don't want to have to change the whole log level to INFO.

`printf` makes sense to me since really all this is for is to print out a realtime view of what's going on when you're executing interactively, not to have things be logged for later.

That said, I don't know what the best practices are.