Switch to a lock for registry updates for better concurrency control
Log msg update
Refactored periodic registry update locking to:
- use a better name for the generational counter
- added additional fine grained locking around the getDelta code path
  to ensure more correct synchronisation
Adding log line for when client is configured to not register with the server
Merge pull request #143 from qiangdavidliu/better-locking

Improved locking for periodic registry refreshes