Add tensorpipe agent tests to multigpu tests. (#49210)
Summary:
Pull Request resolved: https://github.com/pytorch/pytorch/pull/49210
The RPC tests use multiple gpus in some cases (ex: DDP + RPC and Pipe
+ DDP). We should enable multigpu tests for this purpose.
ghstack-source-id: 118366595
Test Plan: waitforbuildbot
Reviewed By: rohan-varma
Differential Revision: D25485506
fbshipit-source-id: eabbf442471ebc700b5986bc751879b9cf72b752
