[TensorPipe] Give higher priority to CPU-only channels. (#56908)
Summary:
Pull Request resolved: https://github.com/pytorch/pytorch/pull/56908
CUDA channels might implement CPU-to-CPU transfers, but will usually be
less efficient for that purpose.
Test Plan: CI
Reviewed By: lw
Differential Revision: D27994069
fbshipit-source-id: fefa7f243eb43cf769864233df518f2a1819f949
