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/packet/IPv4.java b/src/main/java/net/onrc/onos/core/packet/IPv4.java
index 8933203..72efa61 100644
--- a/src/main/java/net/onrc/onos/core/packet/IPv4.java
+++ b/src/main/java/net/onrc/onos/core/packet/IPv4.java
@@ -431,7 +431,7 @@
 
     /**
      * Accepts an IPv4 address and returns of string of the form xxx.xxx.xxx.xxx
-     * ie 192.168.0.1
+     * ie 192.168.0.1.
      *
      * @param ipAddress
      * @return