Monkey patch Variable module to fix FX codegen
Fixes https://github.com/facebookresearch/torchdynamo/issues/82
There is a `torch.auotgrad.variable` function which conflicts with the module class `torch.autograd.variable.Variable`.
@jansel
Pull Request resolved: https://github.com/pytorch/pytorch/pull/76079
Approved by: https://github.com/jansel, https://github.com/albanD
