Allow RPC port and HTTP port to be on different IP addresses for servers

[mtougeron]

It would be nice if the RPC port and HTTP port could be run on different addresses. By default, they both run on 127.0.0.1 but that means that the HTTP API access isn't available outside of the server. If the client_addr is changed, them all consul calls, even simple ones like consul members needs to have the RPC port passed in.

We want to be able to run HTTP on a non-local IP address (it would be a private one that is only accessible via security group rules to keep it as internal traffic only) so that we can query it from machines that are not running consul. But if we do this, we are not able to write simple scripts or run commands without first finding the server's IP address because the consul binary assumes 127.0.0.1 for RPC.