OSD-replication:

- bugfix for issue 78
- replication will send new requests first (max. parallel requests), if the file is written to HDD. so the replication should not cause OutOfMemory-Exceptions through overloading the HDD anymore
- determining if an ObjectSet is empty will be much faster now
- much measurement-stuff is outcommented, probably it is not necessary anymore

git-svn-id: https://xtreemfs.googlecode.com/svn/trunk@1290 f8528748-c2c0-11dd-ba5c-d3b7c2b3b534