Custom metrics over evaluation only

[mannyv]

@LecJackS @GallantWood

Have a look at this topic that might be relevant

Saving checkpoints with good custom_metric using tune.run()

Hi @mannyv Thank you for helping. I have been running Ray 1.2. I repeated test with 1.3 and was able to reproduce your results: 3 checkpoint saved, and the evaluation metric is in the json, but not the csv.