function onDisconnect( child ) {
		return listener;

		/**
		* Callback invoked upon child process disconnect.
		*
		* @private
		*/
		function listener() {
			debug( 'Child process disconnected. pid: %d.', child.pid );
		}
	}
Returns a callback to be invoked upon child process disconnect.

@private
@param {Object} child - child process
@returns {Callback} callback