Enable checkstyle rule for JLS modifier order

JLS specifies a preferred order for modifiers in
declarations.  Enabled this rule and fixed the
problems that it encountered.

Change-Id: I5e8fa3d29f785ced4c61fbb8c7c8b168289f06e2
diff --git a/src/main/java/net/onrc/onos/core/util/Dpid.java b/src/main/java/net/onrc/onos/core/util/Dpid.java
index f66a5d4..1abd0f1 100644
--- a/src/main/java/net/onrc/onos/core/util/Dpid.java
+++ b/src/main/java/net/onrc/onos/core/util/Dpid.java
@@ -14,7 +14,7 @@
 @JsonDeserialize(using = DpidDeserializer.class)
 @JsonSerialize(using = DpidSerializer.class)
 public final class Dpid {
-    private final static long UNKNOWN = 0;
+    private static final long UNKNOWN = 0;
     private final long value;
 
     /**