Refactor IdBlcok: move to core.util package

Change-Id: Ibe0b3fe82d851a6549e33af1e4dc675f47a814b8
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 5bff0e8..78f60b8 100644
--- a/src/main/java/net/onrc/onos/core/registry/ZookeeperRegistry.java
+++ b/src/main/java/net/onrc/onos/core/registry/ZookeeperRegistry.java
@@ -22,6 +22,7 @@
 import net.floodlightcontroller.core.module.IFloodlightService;
 import net.floodlightcontroller.restserver.IRestApiService;
 import net.onrc.onos.core.registry.web.RegistryWebRoutable;
+import net.onrc.onos.core.util.IdBlock;
 import net.onrc.onos.core.util.OnosInstanceId;
 
 import org.apache.commons.lang.NotImplementedException;