Add ability to share file system between tensorflow serving image and tensorflow predictor

[lminer]

Description

Would be nice to be able to write to some location in the TensorflowPredictor that could be accessed from within tensorflow-serving and vice-versa. This is just a docker cli option, no?

Motivation

This would be a way to get around the issue with passing large amounts of data back and forth between the api and tensorflow-serving as recorded here.

[deliahu]

@lminer When running in a cluster, the /mnt path is shared across the containers; let us know if you're able to get it working, and we'll add it to the docs. Thanks for the suggestion!

[lminer]

Huzzah. It works!

[deliahu]

Awesome! I've added a note to the docs in #1802