ep tests: clean shutdown to silence TCPStore/HeartbeatMonitor noise

Add dist.barrier() + dist.destroy_process_group() in a finally block so
non-zero ranks don't poll the TCPStore after rank 0 (the store server)
exits, which produced noisy 'recvValue failed / Connection was likely
closed' stack traces from ProcessGroupNCCL's HeartbeatMonitor.

Also pass device_id to init_process_group in the internode test to
silence 'Guessing device ID based on global rank' warnings.

test/python/ext/ep/test_internode_multirank.py

@@ -38,7 +38,8 @@ def init_dist():
     world_size = int(os.environ["WORLD_SIZE"])
     local_rank = int(os.environ.get("LOCAL_RANK", rank % 8))
     torch.cuda.set_device(local_rank)
-    dist.init_process_group(backend="nccl", world_size=world_size, rank=rank)
+    dist.init_process_group(backend="nccl", world_size=world_size, rank=rank,
+                            device_id=torch.device(f"cuda:{local_rank}"))
     return rank, world_size, local_rank, dist.new_group(list(range(world_size)))
 
 
@@ -381,3 +382,14 @@ if __name__ == "__main__":
         import traceback
         traceback.print_exc()
         sys.exit(1)
+    finally:
+        # Ordered shutdown: barrier so every rank reaches teardown before the
+        # TCPStore server (rank 0) exits, then destroy the PG. Without this,
+        # ProcessGroupNCCL's HeartbeatMonitor on non-zero ranks logs noisy
+        # "recvValue failed / Connection was likely closed" stack traces.
+        if dist.is_initialized():
+            try:
+                dist.barrier()
+            except Exception:
+                pass
+            dist.destroy_process_group()

test/python/ext/ep/test_intranode_multirank.py

@@ -327,3 +327,14 @@ if __name__ == "__main__":
         import traceback
         traceback.print_exc()
         sys.exit(1)
+    finally:
+        # Ordered shutdown: barrier so every rank reaches teardown before the
+        # TCPStore server (rank 0) exits, then destroy the PG. Avoids noisy
+        # "recvValue failed / Connection was likely closed" stack traces from
+        # ProcessGroupNCCL's HeartbeatMonitor.
+        if dist.is_initialized():
+            try:
+                dist.barrier()
+            except Exception:
+                pass
+            dist.destroy_process_group()

test/python/ext/ep/test_low_latency_multirank.py

@@ -308,7 +308,16 @@ if __name__ == "__main__":
     try:
         main()
     finally:
-        try:
-            dist.destroy_process_group()
-        except Exception:
-            pass
+        # Ordered shutdown: barrier so every rank reaches teardown before the
+        # TCPStore server (rank 0) exits, then destroy the PG. Avoids noisy
+        # "recvValue failed / Connection was likely closed" stack traces from
+        # ProcessGroupNCCL's HeartbeatMonitor.
+        if dist.is_initialized():
+            try:
+                dist.barrier()
+            except Exception:
+                pass
+            try:
+                dist.destroy_process_group()
+            except Exception:
+                pass