libtorch-for-puffer

Update the libtorch used in Puffer to v1.8.1.

libtorch for puffer

Back out "[pt1][tensor] Remove caffe2::ShareData" (#15983)

Summary:
Pull Request resolved: https://github.com/pytorch/pytorch/pull/15983

Original commit changeset: 6e4275d02f4c

Reviewed By: supertopher, Yangqing

Differential Revision: D13644123

fbshipit-source-id: 4b15a4c62995c0e68aad58465600409e302e6504