[bug] Fix deadlock with pause resume and collective_rpc (#37024)

Signed-off-by: hao-aaron <ahao@anyscale.com>

vllm/v1/engine/core.py

@@ -1632,7 +1632,11 @@ class DPEngineCoreProc(EngineCoreProc):
         if self.has_coordinator and request_wave != self.current_wave:
             if request_wave > self.current_wave:
                 self.current_wave = request_wave
-            elif not self.engines_running:
+            elif (
+                not self.engines_running
+                and self.scheduler.pause_state == PauseState.UNPAUSED
+            ):
+                self.engines_running = True
                 # Request received for an already-completed wave, notify
                 # front-end that we need to start the next one.
                 self.output_queue.put_nowait(