Fixed bug RECIPES-8: The chef recipe does not support private/hosted chef server

The chef recipe hard coded the validation_client_name to chef-validator. However, the validation_client_name located in the server and client configuration files must match. The naming rule for validation_client_name for private chef is ORGNAME-validator. Thus, chef-validator will not work for private chef, except the organization name is “chef”. For more details, please see https://cloudifysource.atlassian.net/browse/RECIPES-8. Fixed this issue by making validation_client_name configurable in chef.properties.