Improve log messages from helios testing framework

Many of the log messages produced by the testing framework include
the helios job ID. But these IDs are auto-generated and very long,
so they clutter the logs and don't provide much value to the user.
When the use declares a TemporaryJob, they specify the image they
want to deploy, so it's more useful to log the image name.

Changed many of the detailed log messages from info to debug.

When waiting for an image to start, we would only log if the
image is pulling. We now log whatever state it's in, so we
always know the state of things.

The logs look like this at info level:

```
16:17:03.613 [helios-test-runner-0] INFO  c.s.helios.testing.TemporaryJob - Deploying registry:80/spotify/wiggum:0.0.1-SNAPSHOT-e62e3c6.DIRTY (Job fe89e66) to standalone.local.
16:17:04.208 [helios-test-runner-0] INFO  c.s.helios.testing.TemporaryJob - Job state: PULLING_IMAGE
16:17:04.735 [helios-test-runner-0] INFO  c.s.helios.testing.TemporaryJob - Job state: PULLING_IMAGE
16:17:05.248 [helios-test-runner-0] INFO  c.s.helios.testing.TemporaryJob - Job state: PULLING_IMAGE
16:17:14.018 [helios-test-runner-0] INFO  c.s.helios.testing.TemporaryJob - Job state: RUNNING
16:17:14.020 [helios-test-runner-0] INFO  c.s.helios.testing.TemporaryJob - Probing: wiggum @ 192.168.33.10:20001
16:17:14.524 [helios-test-runner-0] INFO  c.s.helios.testing.TemporaryJob - Probing: wiggum @ 192.168.33.10:20001
16:17:15.063 [helios-test-runner-0] INFO  c.s.helios.testing.TemporaryJob - Up: wiggum @ 192.168.33.10:20001
16:17:17.316 [main] INFO  com.spotify.helios.testing.Jobs - Undeploying registry:80/spotify/wiggum:0.0.1-SNAPSHOT-e62e3c6.DIRTY (Job fe89e66) from standalone.local.
```
Hmmm.  You sure you want UNKNOWN here?  IIRC, UNKNOWN is what should be there if the job has been deployed but the agent has yet to act on it.  Though it may be that by the time verifyHealthy is called that if the agent hasn't acted, it's probably time to call things off.