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/packet/BasePacket.java b/src/main/java/net/onrc/onos/core/packet/BasePacket.java
index a47fcfc..3dd6339 100644
--- a/src/main/java/net/onrc/onos/core/packet/BasePacket.java
+++ b/src/main/java/net/onrc/onos/core/packet/BasePacket.java
@@ -104,7 +104,7 @@
         } catch (Exception e) {
             throw new RuntimeException("Could not clone packet");
         }
-        // TODO: we are using serialize()/deserialize() to perform the 
+        // TODO: we are using serialize()/deserialize() to perform the
         // cloning. Not the most efficient way but simple. We can revisit
         // if we hit performance problems.
         byte[] data = this.serialize();