Allow Configuration of Bind Address of Envoy and Diagd Processes

[josuesdiaz]

Currently, Envoy and Diagd processes are always listening on 0.0.0.0, which is all IPv4 addresses.

To assist in creating a workaround for those who want to bind to IPv6 (namely "::"), this change would allow the usage of environment variables AMBASSADOR_DIAGD_BIND_ADDRESS and AMBASSADOR_ENVOY_BIND_ADDRESS to configure how the services are listening.

As well, this change would allow those who want to limit the processes to a specific IP address, rather than all-IPv4 or all-IPv6.

[josuesdiaz]

• @kflynn

[josuesdiaz]

Think we should be all set with this Issue now. Env vars for chaging bind address of processes are:
AMBASSADOR_ENVOY_BIND_ADDRESS
AMBASSADOR_DIAGD_BIND_ADDRESS

For those interested in binding these to all IPv6 addresses, the following values should work
AMBASSADOR_ENVOY_BIND_ADDRESS: "::"
AMBASSADOR_DIAGD_BIND_ADDRESS: "[::]"