fixes the layout for error messages on the update page

Before:
![error-on-update-page-before](https://cloud.githubusercontent.com/assets/245432/3367863/9d214f7e-fb6a-11e3-9812-c188a03694fb.png)

After:
![error-on-update-page-after](https://cloud.githubusercontent.com/assets/245432/3367862/9a865bc4-fb6a-11e3-8984-488479fe41e0.png)


cc @owncloud/designers