Changes made for the cookbook to work with RightScale platform

The following are the changes made.
* Generated `metadata.json` from `metadata.rb`
* Removed unattended upgrades
* Refactored the `driveclient::default` recipe a bit to get rid of subscribes and to use notifies. For some reason, when we bring up 5 or more servers, some servers fail to register for driveclient.
* Get rid of `Chef::Application.fatal!` and use `raise` as the `Chef::Application` is not available with the version of chef we use at RightScale.