Enable checkstyle Javadoc Comment Style rule

Turn on the Javadoc Comment Style rule and fix
any violations that come up.  This is related to
requiring javadoc description comments to end
with a '.'

Change-Id: I19cf1b9f00d3040987e0b4c8b39461e2e0ad66b5
diff --git a/src/main/java/net/onrc/onos/core/topology/PortEvent.java b/src/main/java/net/onrc/onos/core/topology/PortEvent.java
index fdf8f06..1f20f22 100644
--- a/src/main/java/net/onrc/onos/core/topology/PortEvent.java
+++ b/src/main/java/net/onrc/onos/core/topology/PortEvent.java
@@ -3,9 +3,9 @@
 import java.nio.ByteBuffer;
 
 /**
- * Self-contained Port event Object
+ * Self-contained Port event Object.
  * <p/>
- * TODO: We probably want common base class/interface for Self-Contained Event Object
+ * TODO: We probably want common base class/interface for Self-Contained Event Object.
  */
 public class PortEvent {
     public static class SwitchPort {