Fix issues found by FindBugs: SS_SHOULD_BE_STATIC and SIC_INNER_SHOULD_BE_STATIC

http://findbugs.sourceforge.net/bugDescriptions.html#SS_SHOULD_BE_STATIC
http://findbugs.sourceforge.net/bugDescriptions.html#SIC_INNER_SHOULD_BE_STATIC

Change-Id: I9966b69a5a10fecb29725369859f03f606fedadc
diff --git a/src/main/java/net/onrc/onos/core/packet/BPDU.java b/src/main/java/net/onrc/onos/core/packet/BPDU.java
index ce0d9a2..38e979c 100644
--- a/src/main/java/net/onrc/onos/core/packet/BPDU.java
+++ b/src/main/java/net/onrc/onos/core/packet/BPDU.java
@@ -31,7 +31,7 @@
         TOPOLOGY_CHANGE;
     }
 
-    private final long destMac = 0x0180c2000000L; // 01-80-c2-00-00-00
+    private static final long DEST_MAC = 0x0180c2000000L; // 01-80-c2-00-00-00
 
     // TODO - check this for RSTP
     private LLC llcHeader;
@@ -134,6 +134,6 @@
     }
 
     public long getDestMac() {
-        return destMac;
+        return DEST_MAC;
     }
 }