You're supposed to replace {{cluster_data.manager_node_hostname}} with the hostname of the MySQL server, which on Cloudera Live is the Manager Node. If you're using Cloudera Live, you should refer to the copy of the tutorial as linked to in your welcome email. It will resolve all such variables for your specific cluster. The copy on the website is just for informational purposes - the procedure assumes a lot about the cluster, so you should really just use the copy that's on your cluster.