Mild REST API refactoring.

Change-Id: Ieddbbd02328043118ad64077f8eda746eb2b3a9f
diff --git a/web/api/src/main/java/org/onosproject/rest/DevicesWebResource.java b/web/api/src/main/java/org/onosproject/rest/DevicesWebResource.java
index 3f8417b..91668d8 100644
--- a/web/api/src/main/java/org/onosproject/rest/DevicesWebResource.java
+++ b/web/api/src/main/java/org/onosproject/rest/DevicesWebResource.java
@@ -27,6 +27,7 @@
 import java.util.List;
 
 import static com.google.common.base.Preconditions.checkNotNull;
+import static org.onlab.util.Tools.nullIsNotFound;
 import static org.onosproject.net.DeviceId.deviceId;
 
 /**