[ONOS-5924] fix for Cbench test regression

Change-Id: I85c4f3a36510b48df59ebfe1b9caa3164b0ccdab
diff --git a/incubator/api/src/main/java/org/onosproject/incubator/net/virtual/provider/VirtualPacketProvider.java b/incubator/api/src/main/java/org/onosproject/incubator/net/virtual/provider/VirtualPacketProvider.java
index 605f4e6..11c2b00 100644
--- a/incubator/api/src/main/java/org/onosproject/incubator/net/virtual/provider/VirtualPacketProvider.java
+++ b/incubator/api/src/main/java/org/onosproject/incubator/net/virtual/provider/VirtualPacketProvider.java
@@ -34,4 +34,9 @@
      */
     void emit(NetworkId networkId, OutboundPacket packet);
 
+    /**
+     * Starts to deliver packets to virtual packet managers.
+     */
+    void startPacketHandling();
+
 }