Make prefixes optional in listInstanceToString

For libyang, I need a version without prefixes. Side note: the call in
SysrepoAccess would also work without the prefixes, but I'm going to
leave them, so that the functionality doesn't change.

Change-Id: I0c309288ec39ec3f5e835050fb73a5238ebe8e33
diff --git a/src/netconf_access.cpp b/src/netconf_access.cpp
index 2a2fa96..15b79a8 100644
--- a/src/netconf_access.cpp
+++ b/src/netconf_access.cpp
@@ -134,7 +134,7 @@
         if (m_schema->nodeType(source) == yang::NodeTypes::LeafList) {
             sourceNode->insert_attr(yangModule, "value", leafDataToString(relative.m_path.at(".")).c_str());
         } else {
-            sourceNode->insert_attr(yangModule, "key", instanceToString(node->node_module()->name(), relative.m_path).c_str());
+            sourceNode->insert_attr(yangModule, "key", instanceToString(relative.m_path, node->node_module()->name()).c_str());
         }
     }
     doEditFromDataNode(sourceNode);