[openwebnet] Energy meter returns always zero power if no other device has subscribed...

[openwebnet] Energy meter returns always zero power if no other device has subscribed to power measures (#10565)

* add scheduler to start/stop sending instantaneous consumption

Signed-off-by: Conte Andrea <andrea@conte.com>
* added scheduler also in Initialize() in order to start reading data of a newly discovered thing

Signed-off-by: Conte Andrea <andrea@conte.com>
* removed setActivePowerNotificationsTime()  from dispose()

Signed-off-by: Conte Andrea <andrea@conte.com>
* add log in dispose() method

Signed-off-by: Conte Andrea <andrea@conte.com>