ImageNet logging checklist

[yaroslavvb]

Using this bug to track things we need to add logging for in each run. cc @bearpelican

launcher-side:

• instance names of worker machines
• username of person launching the run
• command-line used to start the run
• copy of launcher_nv.py script

worker-side:

• gpu utilization (using something like https://github.com/tensorpack/tensorpack/blob/726747313fb2f189dd195d32087897b16a23be0a/tensorpack/callbacks/prof.py#L22)
• gpu memory usage (from ^^^)
• cpu load (cat /proc/loadavg or dstat)