Use ListInstance typedef in more places

Change-Id: Ic41218a1e09f76d7455816163d9b3ca24b0b94ca
diff --git a/src/sysrepo_access.hpp b/src/sysrepo_access.hpp
index 26d6c80..0ca7587 100644
--- a/src/sysrepo_access.hpp
+++ b/src/sysrepo_access.hpp
@@ -45,7 +45,7 @@
     void copyConfig(const Datastore source, const Datastore destination) 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;
     [[noreturn]] void reportErrors();
 
     std::string fetchSchema(const char* module, const char* revision, const char* submodule);