iterate_comports on Windows sometimes appends an incorrect interface indicator to the location of USB COM ports #802
Description
When calling serial.tools.list_ports.comports() on Windows, the ListPortInfo.location attribute of a USB COM port without multiple interfaces will have the interface number of a previously enumerated port incorrectly applied to it, ':x.0' for example. This is because the variable bInterfaceNumber is set to None in the outer GUID loop, and not the inner device loop.