Map-Reduce: Mapper sometimes receives null value
ISPN-4471 MapReduceTask: memory leak with useIntermediateSharedCache = true
ISPN-4453 MapReduceTask#executeAsynchronously() isn't asynchronous
ISPN-3729 Minimize the number of moved segments for SyncConsistentHashFactory

Based on the original consistent hashing paper, the
NewSyncConsistentHashFactory algorithm doesn't move any segments at all.