Description of problem: When a Receiver has a capacity (e.g. 10) that is less than the number of messages acknowledged in a batch (e.g. 11), the Receiver's dequeue rate drops significantly.


Version-Release number of selected component (if applicable): latest MRG-M 1.3 and 2.0 prerelease RPMs


How reproducible: 100%


Steps to Reproduce:
1. Send messages to a queue
2. Receive messages from queue using get(), with Receiver capacity 10
3. Call session.acknowledge() after every 11th message received
  
Actual results: on my server, can only receive somewhere between 250 and 600 messages/sec


Expected results: much more than 500 or so messages/second.  With capacity 10, batch size 10, I can receive several thousand messages/sec.