* Added new method FlowDatabaseOperation.getFlowSourceDpid() that
  can be used to get the Source Switch DPID

* Added a boolean flag to FlowEventHandler and FlowManager to enable/disable
  the new Flow setup mechanism:
    enableOnrc2014MeasurementsFlows

* Create locally the FlowEventHandler.dbHandler instead of
  reusing the dbHandler from the FlowManager.
  Reusing the dbHandler from the FlowManager might not be thread-safe (??)

* Renamed flag FlowEventHandler.accessDBFlag
  to enableOnrc2014MeasurementsTopology
  (for consistency with the Flow setup-related flag)

* Changed the logic when reading the complete topology from the database:
  if there is a topology-related event, we unconditionally assume
  the topology has been modified. Long-term this might be sub-optimal,
  but gives us the bare-bones behavior we want to measure.

* Reverse the change to Topology.readFromDatabase() to exclude the
  compareTopology() call (see above bullet).

* Fix a bug when cheching whether there is any event to process.
diff --git a/src/main/java/net/onrc/onos/ofcontroller/topology/Topology.java b/src/main/java/net/onrc/onos/ofcontroller/topology/Topology.java
index dedb589..92da9ba 100644
--- a/src/main/java/net/onrc/onos/ofcontroller/topology/Topology.java
+++ b/src/main/java/net/onrc/onos/ofcontroller/topology/Topology.java
@@ -381,17 +381,13 @@
      * Read topology state from the database.
      *
      * @param dbHandler the Graph Database handler to use.
-     * @return true if topology is updated. In other words,
-     * 		topology read from database is different from current topology.
      */
-    public boolean readFromDatabase(GraphDBOperation dbHandler) {
+    public void readFromDatabase(GraphDBOperation dbHandler) {
 	//
 	// Fetch the relevant info from the Switch and Port vertices
 	// from the Titan Graph.
 	//
-    
-	Map<Long,Node> oldNodesMap = nodesMap;
-	nodesMap = new TreeMap<Long,Node>();
+    	nodesMap = new TreeMap<Long,Node>();
 	
 	Iterable<ISwitchObject> activeSwitches = dbHandler.getActiveSwitches();
 	for (ISwitchObject switchObj : activeSwitches) {
@@ -456,7 +452,6 @@
 	    }
 	}
 	dbHandler.commit();
-	return ! compareTopology(oldNodesMap, nodesMap);
     }
     
     // TODO Merge into loops in readFromDatabase() can reduce execution time.