state_dict serialization for Conv2d + some bugfixes
Summary: Pull Request resolved: https://github.com/pytorch/pytorch/pull/24116
Test Plan: Imported from OSS
Reviewed By: eellison
Differential Revision: D16765476
Pulled By: jamesr66a
fbshipit-source-id: 96275cea87d7f5e7de5d1925cbce220066f1a465
