Fix fabric pipeliner add to existing

Change-Id: Ieaea9ec1dd63e938382e9c2e9d3adf88fb5d00a7
diff --git a/pipelines/fabric/src/main/java/org/onosproject/pipelines/fabric/pipeliner/FabricPipeliner.java b/pipelines/fabric/src/main/java/org/onosproject/pipelines/fabric/pipeliner/FabricPipeliner.java
index 93f53db..2ef60ff 100644
--- a/pipelines/fabric/src/main/java/org/onosproject/pipelines/fabric/pipeliner/FabricPipeliner.java
+++ b/pipelines/fabric/src/main/java/org/onosproject/pipelines/fabric/pipeliner/FabricPipeliner.java
@@ -321,6 +321,10 @@
             case REMOVE:
                 flowRules.forEach(ops::remove);
                 break;
+            case ADD_TO_EXISTING:
+            case REMOVE_FROM_EXISTING:
+                // Skip it because we don't need to modify next flow
+                break;
             default:
                 log.warn("Unsupported op {} for {}", objective);
                 fail(objective, ObjectiveError.BADPARAMS);