Add missing final

Change-Id: Icaab9061987e591f981612d355440a53d10a92ce
diff --git a/incubator/store/src/test/java/org/onosproject/incubator/store/virtual/impl/SimpleVirtualMastershipStoreTest.java b/incubator/store/src/test/java/org/onosproject/incubator/store/virtual/impl/SimpleVirtualMastershipStoreTest.java
index 1ad76f2..350fffb 100644
--- a/incubator/store/src/test/java/org/onosproject/incubator/store/virtual/impl/SimpleVirtualMastershipStoreTest.java
+++ b/incubator/store/src/test/java/org/onosproject/incubator/store/virtual/impl/SimpleVirtualMastershipStoreTest.java
@@ -43,7 +43,7 @@
 
 public class SimpleVirtualMastershipStoreTest {
 
-    private static NetworkId VNID1 = NetworkId.networkId(1);
+    private static final NetworkId VNID1 = NetworkId.networkId(1);
 
     private static final DeviceId VDID1 = DeviceId.deviceId("of:01");
     private static final DeviceId VDID2 = DeviceId.deviceId("of:02");