Enable checkstyle trailing spaces rule

Enable the checkstyle rule that detects unneeded trailing spaces
and fix the violations of the rule.

Change-Id: I65567c87142c5a257f0230a55bc4376e770d416f
diff --git a/src/main/java/net/onrc/onos/core/linkdiscovery/ILinkDiscoveryListener.java b/src/main/java/net/onrc/onos/core/linkdiscovery/ILinkDiscoveryListener.java
index 9b237c4..484616e 100644
--- a/src/main/java/net/onrc/onos/core/linkdiscovery/ILinkDiscoveryListener.java
+++ b/src/main/java/net/onrc/onos/core/linkdiscovery/ILinkDiscoveryListener.java
@@ -1,5 +1,5 @@
 /**
- *    Copyright 2011, Big Switch Networks, Inc. 
+ *    Copyright 2011, Big Switch Networks, Inc.
  *    Originally created by David Erickson, Stanford University
  *
  *    Licensed under the Apache License, Version 2.0 (the "License"); you may