Enable checkstyle rule to find empty code blocks

Enabled checkstyle rule that detects empty code blocks and fixed the
violations that were discovered.

Change-Id: Icc23e028f2bbabc1849ec566923aa125b2486a3b
diff --git a/src/main/java/net/onrc/onos/core/topology/TopologyManager.java b/src/main/java/net/onrc/onos/core/topology/TopologyManager.java
index 4788641..d915042 100644
--- a/src/main/java/net/onrc/onos/core/topology/TopologyManager.java
+++ b/src/main/java/net/onrc/onos/core/topology/TopologyManager.java
@@ -773,6 +773,7 @@
         } else {
             // TODO: Update the switch attributes
             // TODO: Nothing to do for now
+            log.debug("Update switch attributes");
         }
         apiAddedSwitchEvents.add(switchEvent);
     }
@@ -828,6 +829,7 @@
             switchImpl.addPort(port);
         } else {
             // TODO: Update the port attributes
+            log.debug("Update port attributes");
         }
         apiAddedPortEvents.add(portEvent);
     }
@@ -942,6 +944,7 @@
                 removeDevice(deviceEvent);
         } else {
             // TODO: Update the link attributes
+            log.debug("Update link attributes");
         }
 
         apiAddedLinkEvents.add(linkEvent);