This is just a cleanup work to hide some of the private state of
ReplSetTest so it is easier to encapsulate and add new logic. Also enables
strict mode.
If you clone a database and a document, due to an update, moves forward in memory, cloner might clone both the old and new document.
When this happens, creating a unique index might fail. This change restarts the clone when this happens, and will abort after 3 failed cloning attempts.
