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/traceng/traceng_vm.py

@@ -348,6 +348,7 @@ class TraceNGVM(BaseNode):
             raise TraceNGError("Port {port_number} doesn't exist in adapter {adapter}".format(adapter=self._ethernet_adapter,
                                                                                               port_number=port_number))
 
+        await self.stop_capture(port_number)
         if self.is_running():
             await self._ubridge_send("bridge delete {name}".format(name="TraceNG-{}".format(self._id)))
 
@@ -409,6 +410,8 @@ class TraceNGVM(BaseNode):
         """
 
         nio = self.get_nio(port_number)
+        if not nio.capturing:
+            return
         nio.stopPacketCapture()
 
         if self.ubridge: