Guard against negative rpcTimeout being passed in to RpcBackendOptions (#38267)
Summary:
Pull Request resolved: https://github.com/pytorch/pytorch/pull/38267
Assert that the rpcTimeout is positive in RpcBackendOptions
constructor
ghstack-source-id: 104029918
Test Plan: CI
Differential Revision: D21509850
fbshipit-source-id: c925490e3d8fa2ffa42b0ae1170ca2f740af11f7
