oob performance improvement for cpu DDP
Signed-off-by: Wang, Yi A <yi.a.wang@intel.com>

# What does this PR do?

oob performance improvement for cpu DDP, currently if no OMP_NUM_THREADS/MKL_NUM_THREADS is set, num_cpu_threads_per_process is set to 1. very slow performance.


## Before submitting
- [ ] This PR fixes a typo or improves the docs (you can dismiss the other checks if that's the case).
- [ ] Did you read the [contributor guideline](https://github.com/huggingface/transformers/blob/main/CONTRIBUTING.md#start-contributing-pull-requests),
      Pull Request section?
- [ ] Was this discussed/approved via a Github issue or the [forum](https://discuss.huggingface.co/)? Please add a link
      to it if that's the case.
- [ ] Did you make sure to update the documentation with your changes? Here are the
      [documentation guidelines](https://github.com/huggingface/transformers/tree/main/docs), and
      [here are tips on formatting docstrings](https://github.com/huggingface/transformers/tree/main/docs#writing-source-documentation).
- [ ] Did you write any new necessary tests?


## Who can review?

- trainer: @sgugger

@yao-matrix @sgugger @liangan1 please help review it<|||||>_The documentation is not available anymore as the PR was closed or merged._<|||||>Hey @sywangyi, thanks for your PR! Sylvain is currently off for a few weeks, we'll merge this PR once he's back.

Thanks for your contribution!