usb-host: reset and close libusb_device_handle before qemu exit

we should perform these things as same as usb_host_close.
Signed-off-by: Nlinzhecheng <linzhecheng@huawei.com>
Message-id: 20181130064700.5984-1-linzhecheng@huawei.com

[ kraxel: whitespace fixup ]
Signed-off-by: NGerd Hoffmann <kraxel@redhat.com>

hw/usb/host-libusb.c

@@ -988,7 +988,9 @@ static void usb_host_exit_notifier(struct Notifier *n, void *data)
 
     if (s->dh) {
         usb_host_release_interfaces(s);
+        libusb_reset_device(s->dh);
         usb_host_attach_kernel(s);
+        libusb_close(s->dh);
     }
 }