Leverage TensorPipe's automatic SHM address selection (#63028)

Leverage TensorPipe's automatic SHM address selection (#63028)

Summary:
Pull Request resolved: https://github.com/pytorch/pytorch/pull/63028

TensorPipe until now required PyTorch to come up and provide a unique identifier to use as address for the UNIX domain socket used in the SHM transport. However the Linux kernel can automatically assign an available address (like it does with IP ports), and TensorPipe now supports it, so we can remove that useless PyTorch logic.

Test Plan: CI

Reviewed By: mrshenli

Differential Revision: D30220352

fbshipit-source-id: 78e8a6ef5916b2a72df26cdc9cd367b9d083e821