Fixed not to print misleading "device does not exist" warning to the log.

Change-Id: I4006c865d7388c6537f6068128bf895a5d3d55e8
diff --git a/core/store/dist/src/main/java/org/onosproject/store/device/impl/GossipDeviceStore.java b/core/store/dist/src/main/java/org/onosproject/store/device/impl/GossipDeviceStore.java
index c770359..de6d2f0 100644
--- a/core/store/dist/src/main/java/org/onosproject/store/device/impl/GossipDeviceStore.java
+++ b/core/store/dist/src/main/java/org/onosproject/store/device/impl/GossipDeviceStore.java
@@ -538,8 +538,9 @@
                     }
                 }
             }
+        } else {
+            log.warn("Device {} does not exist in store", deviceId);
         }
-        log.warn("Device {} does not exist in store", deviceId);
         return null;
     }