virt-manager doesn't delete a NIC on a guest OS

1. Check that a guest OS is running.
# virsh list
Id Name State
----------------------------------
...
4 test01 running
<The guest "test01" is running.>

2. Add a NIC other than virtio to the guest OS by virt-manager.
<The NIC appears on virt-manager.>

3. Delete the NIC from the guest OS by clicking remove button.
<The NIC is deleted on virt-manager.>

4. Shutdown the guest OS by virt-manager.
5. Check the hardware details.
<The NIC remains>