Major Description
Make the SimpleQueueEntryList Iterator clean the list node structure during operation by using the getNextValidEntry() method rather than getNextNode() method.
This will result in the HouseKeeping thread performing cleanup similar to that of the scavenge() process, though far less aggressively. In concert with the message delivery processes now also using getNextValidEntry() this will allow the queue to be more self-cleaning, enabling us to work toward simply removing the explicit scavenge() calls which can hinder performance when using selectors and/or having vast numbers of messages on a queue.