Fix padding of outdated discussion item.

Old:

![Screen_Shot_2015-10-16_at_09.29.17](https://gitlab.com/gitlab-org/gitlab-ce/uploads/d715debebe54d27c2eed7c22843e886c/Screen_Shot_2015-10-16_at_09.29.17.png)

New:

![Screen_Shot_2015-10-16_at_09.29.23](https://gitlab.com/gitlab-org/gitlab-ce/uploads/7c0c033adade92cb16406c027cb4c010/Screen_Shot_2015-10-16_at_09.29.23.png)

It still looks the same when the discussion is expanded.

See merge request !1614