ONOS-7276 OFAgent - fix ItemNotFoundException when processing FLOW_MOD message

Change-Id: I43c21b871dbf128ba97969987311a1c51a1820ae
diff --git a/apps/ofagent/src/main/java/org/onosproject/ofagent/impl/OFAgentVirtualFlowEntryBuilder.java b/apps/ofagent/src/main/java/org/onosproject/ofagent/impl/OFAgentVirtualFlowEntryBuilder.java
index 9ed3a83..eeb7cc5 100644
--- a/apps/ofagent/src/main/java/org/onosproject/ofagent/impl/OFAgentVirtualFlowEntryBuilder.java
+++ b/apps/ofagent/src/main/java/org/onosproject/ofagent/impl/OFAgentVirtualFlowEntryBuilder.java
@@ -33,11 +33,8 @@
     private static final Logger log = LoggerFactory.getLogger(OFAgentVirtualFlowEntryBuilder.class);
     private static final String DRIVER_NAME = "ovs";
 
-    private final DriverHandler driverHandler;
-
     public OFAgentVirtualFlowEntryBuilder(DeviceId deviceId, OFFlowMod fm, DriverService driverService) {
-        super(deviceId, fm, driverService);
-        this.driverHandler = getDriver(deviceId, driverService);
+        super(deviceId, fm, getDriver(deviceId, driverService));
     }
 
     protected static DriverHandler getDriver(DeviceId devId, DriverService driverService) {