Sequencer Writeback Validator - test necessarily fails

[DollyGodet]

In the writeback sequence documentation, it is specified that the state_etag should be included by state and config. In case of an incorrect state_etag in the config, the device should reject the config.
According to this, the WritebackValidator should include the state_etag in the config. At the moment, the sequencer (WritebackValidator) does not include the state_etag in the config to test the writeback, so the test necessarily fails, because the config is rejected by the device.