#810 DeviceProxy.write_attribute_asynch javadoc misses return tag

[Ingvord]

No description for return value:

/**

     * Asynchronous write_attribute.
     *
     * @param attr Attribute value (name, writing value...)
     */
    // ==========================================================================
    public int write_attribute_asynch(DeviceAttribute attr) throws DevFailed {
        return deviceProxyDAO.write_attribute_asynch(this, attr);
    }