Use cases for listen address

Correct cassandra.yaml listen_address settings for various use cases.

Single-node installations: do one of the following:
- Comment out the listen_address property. If the node is properly configured (host name, name resolution, and so on), the database uses InetAddress.getLocalHost() to get the local address from the system.
- Leave the default setting, localhost.
Node in a multi-node installations: set the listen_address property to the node’s IP address or hostname, or set listen_interface.
Node in a multi-network or multi-datacenter installation, within an EC2 environment that supports automatic switching between public and private interfaces: set listen_address to the node’s IP address or hostname, or set listen_interface.
Node with two physical network interfaces in a multi-datacenter installation or cluster deployed across multiple Amazon EC2 regions using the Ec2MultiRegionSnitch:
1. Set listen_address to this node’s private IP or hostname, or set listen_interface (for communication within the local datacenter).
2. Set broadcast_address to the second IP or hostname (for communication between datacenters).
3. Set listen_on_broadcast_address to true.
4. If this node is a seed node, add the node’s public IP address or hostname to the seeds list.
Open the storage_port or ssl_storage_port on the public IP firewall.

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