fused convbn: respect the strict argument when loading from state dict (#39205)
Summary:
Pull Request resolved: https://github.com/pytorch/pytorch/pull/39205
Context:
* https://github.com/pytorch/pytorch/pull/38478 modified convbn folding logic
* https://github.com/pytorch/pytorch/pull/38820 fixed the ^ to be backwards compatible and be able to load v1 state dicts
This PR is an additional fix on backwards compatibility - it allows
older dicts to be loaded with `strict == False`. This is important
because there are teams who use this flow to load floating point
checkpoints into fused models, with `strict == False`
Test Plan:
1. save a floating point and corresponding fused model:
https://gist.github.com/vkuzo/177eba811a7a2ac359054fe9d4e3f099
2. load both of them, it works with strict==False and the floating point
one fails with a good error message with strict==True:
https://gist.github.com/vkuzo/447c9e797f208cb98447ffb24359d73e
Imported from OSS
Differential Revision: D21774353
fbshipit-source-id: f85f0c7fa956561824c9addb9198fea7a76a91aa
