ISPN-4733 Investigate potential issues with System.nanoTime() overflow

* Fixed TestingUtil calculation for when to stop trying
* Changed stats to not error if nanotime is -1 (extreme edge case)
* Also fixed TransactionTable when clearing old txs
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.