Describe the bug
After this commit dd40269, specify max_shard_size to zero_to_fp32.py would generate empty weights

To Reproduce
Use deepspeed v0.16.0

Reason
According to the code https://github.com/microsoft/DeepSpeed/blob/f743feca033515fdded50a98093da5a48eb41e74/deepspeed/utils/zero_to_fp32.py#L513-L529, the state_dict is overrided instead of making a copy, that's why the original state_dict become empty