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/DHCP.java b/src/main/java/net/onrc/onos/core/packet/DHCP.java
index aea1ab1..e2a109e 100644
--- a/src/main/java/net/onrc/onos/core/packet/DHCP.java
+++ b/src/main/java/net/onrc/onos/core/packet/DHCP.java
@@ -51,6 +51,7 @@
      * ------------------------------------------
      * |            options (312)               |
      * ------------------------------------------
+     * Basic packet.
      */
     // Header + magic without options
     public static final int MIN_HEADER_LENGTH = 240;
@@ -279,7 +280,7 @@
     }
 
     /**
-     * Gets a specific DHCP option parameter
+     * Gets a specific DHCP option parameter.
      *
      * @param opetionCode The option code to get
      * @return The value of the option if it exists, null otherwise