OSD-replication:

- replication refactored
- ServiceAvailability moved, because class is common and can be used from others as well, which requires timouts for not reachable services

git-svn-id: https://xtreemfs.googlecode.com/svn/trunk@757 f8528748-c2c0-11dd-ba5c-d3b7c2b3b534