Handle newly created devices cleanly.
Handle newly created devices cleanly.

If no TestJob exists, the call to latest()
fails with a TestJob.DoesNotExist exception.

Change-Id: I599c45d484daff604773b6ecfe806a1df508a49f

Linaro/lava-server,Linaro/lava-server,Linaro/lava-server,Linaro/lava-server