[VOL-936] add changes for onu distance from OLT

Change-Id: If6201799946ac753780d0424c4bd986e2fb394d2
diff --git a/rw_core/core/api/grpc_nbi_handler.go b/rw_core/core/api/grpc_nbi_handler.go
index 0bacb33..3e06cf7 100755
--- a/rw_core/core/api/grpc_nbi_handler.go
+++ b/rw_core/core/api/grpc_nbi_handler.go
@@ -807,6 +807,6 @@
 }
 
 func (handler *NBIHandler) GetExtValue(ctx context.Context, valueparam *voltha.ValueSpecifier) (*voltha.ReturnValues, error) {
-	log.Debugw("GetValue-request", log.Fields{"onu-id": valueparam.Id})
-	return nil, errors.New("UnImplemented")
+	log.Debugw("GetExtValue-request", log.Fields{"onu-id": valueparam.Id})
+	return handler.deviceMgr.GetExtValue(ctx, valueparam)
 }