Revert RRef.to_here()/local_value() return type (#29396)
Summary:
Pull Request resolved: https://github.com/pytorch/pytorch/pull/29396
The return types of RRef.to_here()/local_value() were recently
changed to Future, which triggers flakiness as the RRef could be
deleted before the future.wait() finishes. While we are still
discussing how we'd like to solve it, this commit reverts the
return type to stop bleeding in tests.
closes #28885
Test Plan: Imported from OSS
Differential Revision: D18375571
Pulled By: mrshenli
fbshipit-source-id: 354dbf38b15ab804e44fc9968dd30888415c1fab
