Use ListInstance typedef in more places

Change-Id: Ic41218a1e09f76d7455816163d9b3ca24b0b94ca
diff --git a/src/netconf_access.hpp b/src/netconf_access.hpp
index 964fa54..0cc4eb4 100644
--- a/src/netconf_access.hpp
+++ b/src/netconf_access.hpp
@@ -49,7 +49,7 @@
     std::shared_ptr<Schema> schema() override;
 
 private:
-    std::vector<std::map<std::string, leaf_data_>> listInstances(const std::string& path) override;
+    std::vector<ListInstance> listInstances(const std::string& path) override;
 
     std::string fetchSchema(const std::string_view module, const
             std::optional<std::string_view> revision, const