Add flag to temporarily disable MKL-DNN conv (#23837)
Summary:
Pull Request resolved: https://github.com/pytorch/pytorch/pull/23837
This is a temporary workaround to an issue in MKL-DNN's Convolution backwards implementation: https://github.com/pytorch/pytorch/issues/23825
It is only used to enable testing quantization
Test Plan: Imported from OSS
Differential Revision: D16659081
Pulled By: jamesr66a
fbshipit-source-id: de18ebe98dec2a042f28b23373e20da2b44a42a2
