Revert D27442325: [torch/elastic] Revise the rendezvous handler registry logic.
Test Plan: revert-hammer
Differential Revision:
D27442325 (https://github.com/pytorch/pytorch/commit/df299dbd7d8241669aaac7ce07ed0c034f219b4f)
Original commit changeset: 8519a2caacbe
fbshipit-source-id: f10452567f592c23ae79ca31556a2a77546726b1
