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
Change ReplicatedCHFactory to only replace leavers in updateMembers()

Uneven primary ownership should be dealt with in rebalance() only.
Delegate the isBalanced() check in DefaultRebalancePolicy to the CH factory

Allows waitForRehashToComplete() to work even if the CH factory allocated
less than numOwners owners to each segment.