Client choose the lowest RTT after retrying several times.

Allowed movements are smaller than 10% of the current distance btween nodes.
When sending ping requests, connection might time out after MAX_REQUEST_TIMEOUT_IN_NS.
Completed debug information in OSD side.



git-svn-id: https://xtreemfs.googlecode.com/svn/trunk@1350 f8528748-c2c0-11dd-ba5c-d3b7c2b3b534