[A-MQ6, Composite Topic] memory usage for composite topic grows, even though no subscribers registered on topic

Issue

After message has been forwarded to the underlying queues MemoryUsageByteCount is increasing, we would have expected it to return to zero.

<destinationInterceptors>
          <virtualDestinationInterceptor>
            <virtualDestinations>
                <compositeTopic name="target" forwardOnly="false" concurrentSend="true" >
                         <forwardTo>
                            <queue physicalName="queue.one" />
                            <queue physicalName="queue.two" />
                  </forwardTo>
        </compositeTopic>
           </virtualDestinations>
     </virtualDestinationInterceptor>
</destinationInterceptors>