it provider: produce-transactions does not close itemProducer on success

This is similar to CONTROLLER-1681 but now it does not concern the scenario where producer fails. Instead, when producer finishes successfully, it prevents another produce-transactions call with the same id.

This leads [0] to the same "is attached to producer" error message.

[0] https://logs.opendaylight.org/sandbox/jenkins091/controller-csit-3node-clustering-li-only-carbon/10/log.html.gz#s1-s4-t3-k2-k25-k1-k8