Fix crash issue in conv+sum fusion for MKLDNN on caffe2 (#20139)
Summary:
The isConvFusion(...) is only for Conv op.
If non-Conv op, the crash takes place.
Pull Request resolved: https://github.com/pytorch/pytorch/pull/20139
Differential Revision: D15280604
Pulled By: yinghai
fbshipit-source-id: eb45be11990b3bf7c5b45f02ebb6018444ab5357
