Discover Cassandra nodes via Kubernetes DNS during replication

[c-w]

Currently, the helm chart that sets up Cassandra has nodes discovering each other by IP during data replication. In rare situations we've seen this cause issues if Cassandra and Kubernetes get out of sync as to what are the correct IP addresses for the Cassandra workers. To prevent this issue and shield Cassandra from IP changes, we want to front each Cassandra node with a DNS name of a kubernetes service. @xtophs is the expert in this area for further questions.