Add missing call to DistAutogradContainer::init (#25391)
Summary:
cc pritamdamania87
Pull Request resolved: https://github.com/pytorch/pytorch/pull/25391
Differential Revision: D17113014
Pulled By: mrshenli
fbshipit-source-id: 2de37b832be1dd7a68ecd3576d93d72a960648b5
