PortNumber fixes

- hide new PortNumber(short) and use PortNumber.uint16 instead
- added utility to get PortNumber

Change-Id: Ia39fbe6e7126a3d9465d3035a06850c1d54a7f25
diff --git a/src/main/java/net/onrc/onos/core/packetservice/BroadcastPacketOutNotification.java b/src/main/java/net/onrc/onos/core/packetservice/BroadcastPacketOutNotification.java
index 8a9c065..4f96302 100644
--- a/src/main/java/net/onrc/onos/core/packetservice/BroadcastPacketOutNotification.java
+++ b/src/main/java/net/onrc/onos/core/packetservice/BroadcastPacketOutNotification.java
@@ -92,7 +92,7 @@
             topology.acquireReadLock();
             try {
                 globalPort = topology.getPort(new Dpid(entry.getKey()),
-                    new PortNumber(entry.getValue()));
+                    PortNumber.uint16(entry.getValue()));
             } finally {
                 topology.releaseReadLock();
             }