fix the bug for mkldnn clone (#20943)
Summary:
This PR is to solve the bug for clone a MKLDNN tensor, please see the issue https://github.com/pytorch/pytorch/issues/20895.
Pull Request resolved: https://github.com/pytorch/pytorch/pull/20943
Differential Revision: D15511516
Pulled By: mrshenli
fbshipit-source-id: 05b41d6c7eaf8703521f4c768b8f26ec8501dc5e
