ZK-1931/javazab — pull request #64 by EasonLiao (2014-07-14 05:29:22+00:00)
Title: clean up logging

- Move heartbeat logging from debug to trace. Ideally the log at debug level should be quiet when there is no request going on.
- Use TextFormat.shortDebugString for logging protobuf objects. Otherwise the log message takes up too much space.
- Use MDC to log server ID and possibly server state (looking/leading/following). http://www.slf4j.org/manual.html#mdc