Remove loop_test mode (#46618)
Summary:
Pull Request resolved: https://github.com/pytorch/pytorch/pull/46618
Using D19631971 (https://github.com/pytorch/pytorch/commit/b4b1b100bddf92ab536cac1d05aab84695d06edc) and https://github.com/pytorch/pytorch/pull/32935/files as a reference.
Test Plan:
```
$ buck run glow/fb/test:sparsenn_test -- --gtest_filter='SparseNNTest.vanillaC2' --onnxifi_debug_mode --nocaffe2_predictor_use_memonger
```
Generated dot file https://www.internalfb.com/intern/graphviz/?paste=P146216905
Reviewed By: yinghai
Differential Revision: D24427800
fbshipit-source-id: 7d1d8768352a52af104e0a75ce982c1eb861aa73
