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/apps/proxyarp/ProxyArpManager.java b/src/main/java/net/onrc/onos/apps/proxyarp/ProxyArpManager.java
index 805e657..4691149 100644
--- a/src/main/java/net/onrc/onos/apps/proxyarp/ProxyArpManager.java
+++ b/src/main/java/net/onrc/onos/apps/proxyarp/ProxyArpManager.java
@@ -534,7 +534,7 @@
                 }
 
 //                              BroadcastPacketOutNotification key =
-//                                              new BroadcastPacketOutNotification(eth.serialize(), 
+//                                              new BroadcastPacketOutNotification(eth.serialize(),
 //                                                              target, sw.getId(), pi.getInPort());
 //                              broadcastPacketOutEventChannel.addTransientEntry(eth.getDestinationMAC().toLong(), key);
             } else {