NETCONF: list instance queries should hit the ops tree as well

getItems() operates on config and operation data, not just on the config
data. It is possible that there are lists which only live in an ops data
subtree.

Change-Id: I0206290dfcc4c1ebe91b4728f8e7a9230fc387cb
diff --git a/tests/example-schema.yang b/tests/example-schema.yang
index 5ef67d5..ac7724a 100644
--- a/tests/example-schema.yang
+++ b/tests/example-schema.yang
@@ -209,4 +209,9 @@
             }
         }
     }
+
+    leaf temperature {
+        type int32;
+        config false;
+    }
 }