Fix ClassCastException

Change-Id: I1c9e6a37c6871bd8186d5ab19a87268d9250aacd
diff --git a/drivers/default/src/main/java/org/onosproject/driver/pipeline/SpringOpenTTP.java b/drivers/default/src/main/java/org/onosproject/driver/pipeline/SpringOpenTTP.java
index 6dab296..049e0c5 100644
--- a/drivers/default/src/main/java/org/onosproject/driver/pipeline/SpringOpenTTP.java
+++ b/drivers/default/src/main/java/org/onosproject/driver/pipeline/SpringOpenTTP.java
@@ -1093,7 +1093,7 @@
      * case, we refer to this as a dummy group.
      *
      */
-    private class SpringOpenGroup implements NextGroup {
+    protected class SpringOpenGroup implements NextGroup {
         private final boolean dummy;
         private final GroupKey key;
         private final TrafficTreatment treatment;