Summary:
We were running into a problem where a Job could not be pickled. It needs to be pickled in order for the master flow operator to execute it using the session.
This creates a concept of "compiled" Job, that pretty much only stores protobufs with the Jobs to be executed, avoiding any issue with pickling.
Reviewed By: dzhulgakov
Differential Revision: D4554799
fbshipit-source-id: 2ee9877ca49a796d51925e5ec917436e3d930984