GitLab

Summary:
Add support in d2go.distributed for `env://` init method. Use env variables as specified in https://pytorch.org/docs/stable/distributed.html#environment-variable-initialization for initialized distributed params.

Also change train_net cli function signature to accept args list instead of only using `sys.argv`. To allow calling this function from AIEnv launcher.

Differential Revision: D34540275

fbshipit-source-id: 7f718aed4c010b0ac8347d43b5ca5b401210756c