Added a health discovery service config option in bootstrap.proto.
There is skeleton code for this service in source/common/upstream/health_discovery_service.cc
and an integration test that tests connectivity between envoy running hds and a management server.
This work is for #1310.
Risk Level: Low
Signed-off-by: Lilika Markatou <lilika@google.com>
Mirrored from https://github.com/envoyproxy/envoy @ 1413d5697c9a6c5c43d7b3d23bdab23cc8c2604b