config: Update remote URL handling.

logdog/api/endpoints/coordinator/services/v1/service.proto

Index: logdog/api/endpoints/coordinator/services/v1/service.proto
diff --git a/logdog/api/endpoints/coordinator/services/v1/service.proto b/logdog/api/endpoints/coordinator/services/v1/service.proto
index f440950ff77e75e3c0191ffe9fe4b2da7217e27d..4315331477c6716c3592b822729e9634ec9bcccd 100644
--- a/logdog/api/endpoints/coordinator/services/v1/service.proto
+++ b/logdog/api/endpoints/coordinator/services/v1/service.proto
@@ -21,6 +21,10 @@ message GetConfigResponse {
   string config_set = 2;
   // The path of the text-serialized service configuration protobuf.
   string service_config_path = 3;
+
+  // The host name of the configuration service. This is preferred to
+  // "config_service_url".
+  string config_service_host = 4;
 }
 
 // RegisterStreamRequest is the set of caller-supplied data for the