Update scatter_reduce_ test with parallel backend check (#118708)
**Summary**
Follow up of https://github.com/pytorch/pytorch/pull/118278, in which new added UT `test_scatter_using_atomic_add` failed with `native parallel backend` as reported in https://github.com/pytorch/pytorch/issues/118518.
Pull Request resolved: https://github.com/pytorch/pytorch/pull/118708
Approved by: https://github.com/jgong5, https://github.com/jansel, https://github.com/lezcano
