'model-metadata.json' not saved in GCS

[sverdrup-999]

The 'model-metadata.json' file is not saved in GCS after a full GAME run.

Here is the code that runs it.

This prevents from doing warm-start training as the prior run's file is needed.

Please fix. Thanks!

[ashelkovnykov]

This is being worked on right now. No ETA - it's being merged into a PR with other commits that seek to resolve a different error with the model-metadata.json code.