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
Revert "Revert rebalancing per cache"

This reverts commit 8cbba22ae625c7dd3e8f5ff389b71f4b49aec2b4.