Fix issues found by FindBugs: ST_WRITE_TO_STATIC_FROM_INSTANCE_METHOD

http://findbugs.sourceforge.net/bugDescriptions.html#ST_WRITE_TO_STATIC_FROM_INSTANCE_METHOD

Change-Id: I6a2c7b9e47f8933c77e42cea355c77406485beb9
diff --git a/src/main/java/net/onrc/onos/core/registry/ZookeeperRegistry.java b/src/main/java/net/onrc/onos/core/registry/ZookeeperRegistry.java
index 504e661..070850d 100755
--- a/src/main/java/net/onrc/onos/core/registry/ZookeeperRegistry.java
+++ b/src/main/java/net/onrc/onos/core/registry/ZookeeperRegistry.java
@@ -96,8 +96,10 @@
     // instead of a ramdon generator.
     //
     private static Random randomGenerator = new Random();
-    private static int nextUniqueIdPrefix = 0;
-    private static int nextUniqueIdSuffix = 0;
+    private static long nextUniqueIdPrefix = 0;
+    // NOTE: The 0xffffffffL value is used by the Unique ID generator for
+    // initialization purpose.
+    private static long nextUniqueIdSuffix = 0xffffffffL;
 
     private final BlockingQueue<SwitchLeaderEvent> switchLeadershipEvents =
             new LinkedBlockingQueue<SwitchLeaderEvent>();
@@ -502,7 +504,7 @@
         } else {
             nextUniqueIdSuffix++;
         }
-        long result = (long) nextUniqueIdPrefix << 32;
+        long result = nextUniqueIdPrefix << 32;
         result = result | (0xffffffffL & nextUniqueIdSuffix);
         return result;
     }
@@ -550,12 +552,6 @@
         }
         log.info("Setting Zookeeper connection string to {}", this.connectionString);
 
-        //
-        // Initialize the Unique ID generator
-        // TODO: This must be replaced by Zookeeper-based allocation
-        //
-        nextUniqueIdPrefix = randomGenerator.nextInt();
-
         restApi = context.getServiceImpl(IRestApiService.class);
 
         switches = new ConcurrentHashMap<String, SwitchLeadershipData>();