Do not initialize `torch.distributed` process group if one is already initailized
Author: Yard1
Pull request: yes

# What does this PR do?

If a `torch.distributed` process group is already initialized, `TrainingArguments` will not initialize one by itself. This allows for the user to create their own custom process groups if needed.

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Fixes # (issue)


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Comments:
cc @sgugger 

_The documentation is not available anymore as the PR was closed or merged._