OSD-replication:

- LRU cache for completely replicated files (so already collected infos could be reused later, if new requests arrive)
- ReplicationStressTest refactored and extended

git-svn-id: https://xtreemfs.googlecode.com/svn/trunk@855 f8528748-c2c0-11dd-ba5c-d3b7c2b3b534