This is being added so that metrics sent to HCP can be augmented with the source node's ID.
Opting not to add this to stats_tag out of caution, since it would increase the cardinality of metrics emitted by Envoy for all users.
There is no functional impact to Envoy expected from this change.
* Add support for envoy readiness flags
- add flags 'envoy-ready-bind-port` and `envoy-ready-bind-addr` on consul connect envoy to create a ready listener on that address.
Dan Stough