Use ListInstance typedef in more places

Change-Id: Ic41218a1e09f76d7455816163d9b3ca24b0b94ca
diff --git a/src/parser_context.hpp b/src/parser_context.hpp
index 88dc71a..2a5ba22 100644
--- a/src/parser_context.hpp
+++ b/src/parser_context.hpp
@@ -32,7 +32,7 @@
 
     // When parsing list suffixes, this path is used to store the path of the list whose keys are being parsed.
     dataPath_ m_tmpListPath;
-    std::map<std::string, leaf_data_> m_tmpListKeys;
+    ListInstance m_tmpListKeys;
 
     bool m_errorHandled = false;
     bool m_completing = false;