[main.py] Part-1/2, Do not pass args command into functions

[ntadimeti]

Pass explicit arguments into functions instead of passing args. All except infer_worker, eval_worker and train_worker are changed so that they accept explicit input arguments.

The *_workers are not changed because the list of arguments they need is very big and we would need a data structure (may be a dict) to zip those arguments together. This will be addressed in another PR.

[tijyojwad]

These are some changes for #48