Fix mail upgradesteps (to3401 and to3402)

With the current implementation, the new behaviors gets doubled in the FTI behaviors list
and makes some troubles when transporting to another clients (see `opengever.ogds.base.transporter`).

![ddd](https://cloud.githubusercontent.com/assets/485755/5122603/d80a1000-70a2-11e4-85b6-7e7a25f1d410.png)

@lukasgraf please have a look ...