Adding CentOS 7 Support to the 389 Server Cookbook

While trying to build a 389 directory server using the Riot Games cookbook, I discovered that it didn’t fully support CentOS 7. I took the liberty of making the necessary modifications to allow a Chef run to complete successfully:

The changes are available in my fork of Riot’s cookbook (the centos7_support branch) and I’ve raised a PR, so hopefully this can be merged into the original cookbook.