-Fixed several bugs in xtfs_vivaldi (testing code)

-Now, OSDs recalculate their position every minute and they update their knownOSDs list every 20 min.



git-svn-id: https://xtreemfs.googlecode.com/svn/trunk@1265 f8528748-c2c0-11dd-ba5c-d3b7c2b3b534