[pytorch] Fix loading from checkpoint after "maximize" flag was introduced in SGD (#68733)
Summary:
After 'maximize' flag was introduced in https://github.com/pytorch/pytorch/issues/46480 some jobs fail because they resume training from the checkpoints.
After we load old checkpoints we will get an error during optimizer.step() call during backward pass in [torch/optim/sgd.py", line 129] because there is no key 'maximize' in the parameter groups of the SGD.
To circumvent this I add a default value `group.setdefault('maximize', False)` when the optimizer state is restored.
Pull Request resolved: https://github.com/pytorch/pytorch/pull/68733
Reviewed By: albanD
Differential Revision: D32480963
Pulled By: asanakoy
fbshipit-source-id: 4e367fe955000a6cb95090541c143a7a1de640c2
