[Broker-J] Remove producer on link destruction

In some test scenarios following error is thrown on the client side:

proton._utils.LinkDetached: sender c83ab7c1-a1f4-4d3d-b7f9-527fabf9e9dd-broadcast to broadcast closed due to: Condition('amqp:internal-error', 'Child of type ProducerImpl already exists with name of c83ab7c1-a1f4-4d3d-b7f9-527fabf9e9dd-broadcast')

It seems, that producer is closed after calling sender.close() on the client side, but still remains to be a child of an appropriate AMQP session in closed state, preventing producer with the same name to be created. StandardReceivingLinkEndpoint#destroy() should be extended with the producer removal.