Async notification handler for the XML-RPC channel boot.
This async handler is used by:
|booted_channel ||The channel already booted or NULL if something have happened.|
|status ||The status value for the XML-RPC boot process request, VortexOk if boot was ok, VortexError if something have happened.|
|message ||A textual diagnostic message reporting current status.|
|user_data ||User space data defined at the function requesting this handler. |