Fix remote packet capture and make sure packet capture is stopped when deleting an NIO. Fixes https://github.com/GNS3/gns3-gui/issues/2753

gns3server/compute/iou/iou_vm.py

@@ -1315,6 +1315,8 @@ class IOUVM(BaseNode):
         """
 
         nio = self.get_nio(adapter_number, port_number)
+        if not nio.capturing:
+            return
         nio.stopPacketCapture()
         log.info('IOU "{name}" [{id}]: stopping packet capture on {adapter_number}/{port_number}'.format(name=self._name,
                                                                                                          id=self._id,