Leave app_desc untouched before writing in token file (function _writefile_app_token)
otherwise creating a Freebox instance twice in a row will fail
(the app_desc read from the file will be different from the one
in memory since it has been changed before writing the auth file)
Leave app_desc untouched before writing in token file (function _writefile_app_token) otherwise creating a Freebox instance twice in a row will fail (the app_desc read from the file will be different from the one in memory since it has been changed before writing the auth file)