use fully qualified name for ScriptClasses (#19239)
Summary:
Pull Request resolved: https://github.com/pytorch/pytorch/pull/19239
ghimport-source-id: 830aad6dc11d2a7247760a9c7c9fc8556f70a706
Differential Revision: D14928293
Reviewed By: eellison
Pulled By: suo
fbshipit-source-id: d2efa5d7f7397526083278d6650b9cee8d967b1a
