Not enough values to unpack in sock.getsockname()

https://github.com/pytorch/torchsnapshot/blob/e8a1fc097b4138493f05e5cac986730d116d0063/torchsnapshot/dist_store.py#L69

```
    master_addr, master_port, _, _ = sock.getsockname()
    ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
ValueError: not enough values to unpack (expected 4, got 2)
```