mod_pubsub: Fix choice of node config defaults

Ignore node plugin defaults if the plugin handling the request isn't
enabled, rather than ignoring 'default_node_config' options and
applying plugin defaults in that case.

src/mod_pubsub.erl

@@ -3371,7 +3371,7 @@ node_options(Host, Type) ->
     case lists:member(Type, config(Host, plugins)) of
 	true ->
             merge_config([ConfigOpts, DefaultOpts]);
-	false -> DefaultOpts
+	false -> ConfigOpts
     end.
 
 -spec node_plugin_options(host(), binary()) -> [{atom(), any()}].