Mild REST API refactoring.

Change-Id: Ieddbbd02328043118ad64077f8eda746eb2b3a9f
diff --git a/web/api/src/main/java/org/onosproject/rest/ClusterWebResource.java b/web/api/src/main/java/org/onosproject/rest/ClusterWebResource.java
index 5f2fde9..7f15bdc 100644
--- a/web/api/src/main/java/org/onosproject/rest/ClusterWebResource.java
+++ b/web/api/src/main/java/org/onosproject/rest/ClusterWebResource.java
@@ -33,6 +33,8 @@
 import java.util.HashSet;
 import java.util.List;
 
+import static org.onlab.util.Tools.nullIsNotFound;
+
 /**
  * REST resource for interacting with the ONOS cluster subsystem.
  */