Try to fix interop test failure

waku/factory/waku.nim

@@ -543,6 +543,10 @@ proc stop*(waku: Waku): Future[Result[void, string]] {.async: (raises: []).} =
     if not waku.wakuDiscv5.isNil():
       await waku.wakuDiscv5.stop()
 
+    if not waku.deliveryService.isNil():
+      await waku.deliveryService.stopDeliveryService()
+      waku.deliveryService = nil
+
     if not waku.node.isNil():
       await waku.node.stop()
 

waku/node/delivery_service/delivery_service.nim

@@ -42,5 +42,5 @@ proc startDeliveryService*(self: DeliveryService) =
   self.recvService.startRecvService()
 
 proc stopDeliveryService*(self: DeliveryService) {.async.} =
-  self.sendService.stopSendService()
+  await self.sendService.stopSendService()
   await self.recvService.stopRecvService()

waku/node/delivery_service/recv_service/recv_service.nim

@@ -193,5 +193,7 @@ proc stopRecvService*(self: RecvService) {.async.} =
   MessageReceivedInternalEvent.dropListener(self.brokerCtx, self.internalMsgListener)
   if not self.msgCheckerHandler.isNil():
     await self.msgCheckerHandler.cancelAndWait()
+    self.msgCheckerHandler = nil
   if not self.msgPrunerHandler.isNil():
     await self.msgPrunerHandler.cancelAndWait()
+    self.msgPrunerHandler = nil

waku/node/delivery_service/send_service/send_service.nim

@@ -250,9 +250,9 @@ proc serviceLoop(self: SendService) {.async.} =
 proc startSendService*(self: SendService) =
   self.serviceLoopHandle = self.serviceLoop()
 
-proc stopSendService*(self: SendService) =
+proc stopSendService*(self: SendService) {.async.} =
   if not self.serviceLoopHandle.isNil():
-    discard self.serviceLoopHandle.cancelAndWait()
+    await self.serviceLoopHandle.cancelAndWait()
 
 proc send*(self: SendService, task: DeliveryTask) {.async.} =
   assert(not task.isNil(), "task for send must not be nil")