fpi-device: Only mark a device as closed if the operation succeeded

We may fail during the close phase, in such case the device should not be
marked as closed.

tests/test-fpi-device.c

@@ -386,6 +386,7 @@ test_driver_close_error (void)
   g_assert (fake_dev->last_called_function == dev_class->close);
   g_assert_error (error, FP_DEVICE_ERROR, FP_DEVICE_ERROR_GENERAL);
   g_assert (error == g_steal_pointer (&fake_dev->ret_error));
+  g_assert_true (fp_device_is_open (device));
 }
 
 static void