[BugFix][DP] Send DP wave completion only from `dp_rank==0` (#18502)

Signed-off-by: Nick Hill <nhill@redhat.com>
Co-authored-by: kourosh hakhamaneshi <kourosh@anyscale.com>

vllm/v1/engine/core.py

@@ -701,7 +701,7 @@ class DPEngineCoreProc(EngineCoreProc):
             for i in range(local_dp_rank * world_size, (local_dp_rank + 1) *
                            world_size))
 
-        self.local_dp_rank = local_dp_rank
+        self.dp_rank = dp_rank
         self.dp_group = vllm_config.parallel_config.stateless_init_dp_group()
         self.current_wave = 0
 
@@ -774,7 +774,7 @@ class DPEngineCoreProc(EngineCoreProc):
                 local_unfinished_reqs)
 
             if not self.engines_running:
-                if self.local_dp_rank == 0:
+                if self.dp_rank == 0:
                     # Notify client that we are pausing the loop.
                     logger.debug("Wave %d finished, pausing engine loop.",
                                  self.current_wave)