Log clientID and requestID. Properly handle async requests in kv.
Reenable sending partial log for recovery
Removed uri when send messages in vr.go. Cancel uncommited operations during recovery.
Receive messages by registering callbacks with Messenger.
Flush log writes.
Fixed heartbeat timer.
Update OpNumber during VR initialization. Truncate file with coldstart flag.
Multiple bug fixes for view change & recovery
Avoid writing duplicate logs during initialization. Avoid appending the full log during starting new view.