Fix bug where the values of keys could change

Change-Id: I34993c413c3f928690701a055ec38c1e7029b473
diff --git a/core/api/src/main/java/org/onosproject/net/intent/Key.java b/core/api/src/main/java/org/onosproject/net/intent/Key.java
index 44c36e0..7007f75 100644
--- a/core/api/src/main/java/org/onosproject/net/intent/Key.java
+++ b/core/api/src/main/java/org/onosproject/net/intent/Key.java
@@ -90,7 +90,7 @@
     private static final class LongKey extends Key {
 
         private final ApplicationId appId;
-        private static long key;
+        private final long key;
 
         private LongKey(long key, ApplicationId appId) {
             super(HASH_FN.newHasher()