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/DevicesListCommand.java b/cli/src/main/java/org/onlab/onos/cli/net/DevicesListCommand.java
index 9a90ef2..357d005 100644
--- a/cli/src/main/java/org/onlab/onos/cli/net/DevicesListCommand.java
+++ b/cli/src/main/java/org/onlab/onos/cli/net/DevicesListCommand.java
@@ -29,12 +29,11 @@
     };
 
     @Override
-    protected Object doExecute() throws Exception {
+    protected void execute() {
         DeviceService service = getService(DeviceService.class);
         for (Device device : getSortedDevices(service)) {
             printDevice(service, device);
         }
-        return null;
     }
 
     /**