onnx/caffe2 tests: Do not execute models with CPU-only operators on GPU.
Summary: Pull Request resolved: https://github.com/pytorch/pytorch/pull/20720
Reviewed By: bddppq
Differential Revision: D15422322
Pulled By: houseroad
fbshipit-source-id: c79795434157ff5f0a7b2774fd40edc71cf35ba7
