Fix groupings not being properly resolved

Change-Id: I878ea328acd4e01ec5ea2a7d5a28b22350bb11bd
Bug: https://tree.taiga.io/project/jktjkt-netconf-cli/issue/116
Bug: https://tree.taiga.io/project/jktjkt-netconf-cli/issue/95
diff --git a/src/yang_schema.cpp b/src/yang_schema.cpp
index bab4715..3512baf 100644
--- a/src/yang_schema.cpp
+++ b/src/yang_schema.cpp
@@ -284,9 +284,7 @@
         const auto absolutePath = "/" + pathToAbsoluteSchemaString(path);
         const auto set = m_context->find_path(absolutePath.c_str());
         const auto schemaSet = set->schema();
-        for (auto it = (*schemaSet.begin())->child(); it; it = it->next()) {
-            nodes.push_back(it);
-        }
+        nodes = (*schemaSet.begin())->child_instantiables(0);
     }
 
     for (const auto node : nodes) {