Fixed a number of CLI commands.
Refactored the StoreService/Manager stuff for common serializer pool.
diff --git a/cli/src/main/java/org/onlab/onos/cli/net/TopologyCommand.java b/cli/src/main/java/org/onlab/onos/cli/net/TopologyCommand.java
index 6c141ae..a258205 100644
--- a/cli/src/main/java/org/onlab/onos/cli/net/TopologyCommand.java
+++ b/cli/src/main/java/org/onlab/onos/cli/net/TopologyCommand.java
@@ -28,11 +28,10 @@
     }
 
     @Override
-    protected Object doExecute() throws Exception {
+    protected void execute() {
         init();
         print(FMT, topology.time(), topology.deviceCount(), topology.linkCount(),
               topology.clusterCount(), topology.pathCount());
-        return null;
     }
 
 }