Show only processes owned by the GitLab user on the Admin-Sidekiq page

(See the Pull-Request #5191)

**Before:**
![bildschirmfoto von 2013-10-16 08 58 22](https://f.cloud.github.com/assets/327488/1340466/23b9d75e-3631-11e3-9139-4cdc806e8e27.png)

**After:**
![bildschirmfoto von 2013-10-16 09 04 26](https://f.cloud.github.com/assets/327488/1340474/41d06d20-3631-11e3-96a8-cf495b6ceea6.png)