servers:

* fixed issue in BufferPool that allowed parent buffers to be returned more than once if view buffers exist
* added more stack trace recording information to BufferPool in order to detect lost buffers
* fixed 'finalized but not freed before' problems if requests were rejected by an OSD stage as a consequence of overload
* fixed bug in RPCNIOSocketServer that could cause an NPE if a write was received after having already closed the connection
* minor fix in Java client


git-svn-id: https://xtreemfs.googlecode.com/svn/trunk@2839 f8528748-c2c0-11dd-ba5c-d3b7c2b3b534