Fixed an minor spacing issue
Re-organized source code in Chef Module

* Re-organized the source code to improve the maintainability.
* Attempted to fix the undeterministic 404/409 data bag error,
which is possibly due to inconsistency between local cache and
states in Chef Server. In particular, we removed cache for Chef
Node and Chef Databag.
* Used the Rest API (instead of Knife command) to delete Chef Node
and Chef API client. The goal is to improve performance.
* Used Rails Logger instead of directly printing to console
* Decrease the max of sleep time before executing the Chef command.