Reconfiguration only works once after HA restart

[kamaradclimber]

When trying to add "new" sensors, the sequence works only once after HA restart.

Scenario:

• add integration, restart HA
• configure the integration with default settings
• reconfigure the integration to add a new sensor => it works as expected
• reconfigure the integration to add another sensor => nothing happens (but not error is triggered, we get information that update proceeded correctly)

This behavior seemed to have appeared with https://github.com/kamaradclimber/rte-ecowatt/pull/31 but I can't explain it so far.