[RPC tests] Run DdpUnderDistAutogradTest and DdpComparisonTest with fork too (#42528)
Summary:
Pull Request resolved: https://github.com/pytorch/pytorch/pull/42528
It seems it was an oversight that they weren't run. This allows to simplify our auto-generation logic as now all test suites are run in both modes.
ghstack-source-id: 109229969
Test Plan: CI
Reviewed By: pritamdamania87
Differential Revision: D22922151
fbshipit-source-id: 0766a6970c927efb04eee4894b73d4bcaf60b97f
