Wip 7539

To track down the EC pool leak, I instrumented the bufferptr constructors to track each unique buffer::raw reference and keep a backtrace for when each was acquired.  I then added a asok hook to dump the live refs and associated backtraces.  The last patch 62fd382 appears to be the actual culprit: we were keeping the entire MOSDECSubWrite in memory until the associated log entry was trimmed.  The other patches are other buffers I noticed were being kept around by the OpTracker mechanism which probably can be disposed of a bit earlier.