Fixed the error of generator in the RandomSampler. (#52956)
Summary:
In `__iter__` of the `RandomSampler`, when `self.replacement` is `False` in the original code, `self.generator` is always used in the `torch.randperm` instead of the generator we set.
Fixes https://github.com/pytorch/pytorch/issues/52568
Pull Request resolved: https://github.com/pytorch/pytorch/pull/52956
Reviewed By: mruberry
Differential Revision: D26724303
Pulled By: H-Huang
fbshipit-source-id: 86f2795c76f3548e31181fb077af046078a173cb
