…se default way to provide backwards compatability.

This commit fixes backwards compatibility after a regressions introduced in !109.

Following test results prove it works:

https://nexedi.erp5.net/test_result_module/20161104-7A7E676

https://nexedi.erp5.net/test_result_module/20161104-15D828A5

/reviewed-on nexedi/slapos!112