[Batch] Long process cleanup time at the end of training jobs

When using clusters (whether orchestrated by AWS Batch or EC2), we are experiencing prolonged delays when disconnecting torch.distributed connections. Since this can be influenced by various factors, it's important to explore optimizations at both the configuration and code levels.

Start by reproducing the prolonged cleanup at the end of training jobs on AWS Batch or EC2 clusters, then investigate torch.distributed disconnect behavior and relevant configuration options. Done means identifying and implementing validated configuration or code optimizations that reduce the delay, with evidence from the affected cluster environments.

Written by the indexing model from the issue text.