Major Description
The JIRA is to check in changes to address performance issues found during my performance testing as following:
1) When WALEdits belongs to a region which split/merged later, replay incurs extra waitUntilRegionOnline RPC call
2) Using a single shared connection for replaying achieves better performance. Everytime creating a new connection, it incurs 4+ seconds to establish a connection to ZK.
3) other small modifications to mitigate excessive logging