[NCCL] Don't override waitUntilInitialized's setting of `comm->init…

…ialized_` (pytorch#136155)

pytorch#133630 sets `initialized_` to `true` which causes previous wait codepaths to skip necessary waits, see also #pytorch#136151

CC @shuqiangzhang @wconstab

Pull Request resolved: pytorch#136155
Approved by: https://github.com/fduwjj, https://github.com/kwen2501, https://github.com/c-p-i-o, https://github.com/shuqiangzhang

torch/csrc/distributed/c10d/NCCLUtils.cpp

@@ -84,7 +84,9 @@ std::shared_ptr<NCCLComm> NCCLComm::split(
       std::nullopt);
   ++source->ncclCommSplitCounter_;
   comm->rank_ = rank;
-  comm->initialized_ = true;
+  if (!nccl_use_nonblocking()) {
+    comm->initialized_ = true;
+  }
   return comm;
 }
 #endif