[FIXED JENKINS-20610] symlink FileAlreadyExistsException

Retrying 3 times while waiting for 100 millis between retries (at
recreating symlink after "deleting" it). Ends up throwing FAE exception
if thrown for a 4th time in a row - as not much can be done at that
point. A warning is logged in that case, prior to throwing the last FAE.