[VOL-4293] OpenONU Adapter update for gRPC migration

Change-Id: I05300d3b95b878f44576a99a05f53f52fdc0cda1
diff --git a/vendor/go.etcd.io/etcd/etcdserver/api/v3rpc/rpctypes/md.go b/vendor/go.etcd.io/etcd/etcdserver/api/v3rpc/rpctypes/md.go
index 5c590e1..90b8b83 100644
--- a/vendor/go.etcd.io/etcd/etcdserver/api/v3rpc/rpctypes/md.go
+++ b/vendor/go.etcd.io/etcd/etcdserver/api/v3rpc/rpctypes/md.go
@@ -17,4 +17,6 @@
 var (
 	MetadataRequireLeaderKey = "hasleader"
 	MetadataHasLeader        = "true"
+
+	MetadataClientAPIVersionKey = "client-api-version"
 )