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/linkdiscovery/NodePortTuple.java b/src/main/java/net/onrc/onos/core/linkdiscovery/NodePortTuple.java
index 224ca3a..c586ecc 100644
--- a/src/main/java/net/onrc/onos/core/linkdiscovery/NodePortTuple.java
+++ b/src/main/java/net/onrc/onos/core/linkdiscovery/NodePortTuple.java
@@ -19,7 +19,7 @@
     protected short portId; // switch port id
 
     /**
-     * Creates a NodePortTuple
+     * Creates a NodePortTuple.
      *
      * @param nodeId The DPID of the switch
      * @param portId The port of the switch
@@ -91,7 +91,7 @@
     /**
      * API to return a String value formed wtih NodeID and PortID
      * The portID is a 16-bit field, so mask it as an integer to get full
-     * positive value
+     * positive value.
      *
      * @return
      */