[DeviceMesh] Temporarily disable re-use subgroup (#118940)
Summary:
The reuse subgroup logic is causing GLOO to timeout on two internal modelstore tests (relevant tests in test plan).
We temporarily disabling re-use subgroup during root-causing to allow the internal tests to be able to run again, as they are now omitted shown in T176426987.
Test Plan:
CI
Pull Request resolved: https://github.com/pytorch/pytorch/pull/118940
Approved by: https://github.com/wanchaol
