Fixed spacing of RTL icon in discussion

The search icon is misplaced in RTL platform:

English (OK)
--
![discussion-en](https://cloud.githubusercontent.com/assets/645156/4899668/ab7609b2-641e-11e4-9c30-b49f06254fc9.png)

Arabic (Before, not broken)
--
![rtl-arabic-before](https://cloud.githubusercontent.com/assets/645156/4899676/bcfb5020-641e-11e4-8d3f-9fda06d908f5.png)

Arabic (After, fixed)
--
![discussion-after](https://cloud.githubusercontent.com/assets/645156/4899691/dd456186-641e-11e4-8fb1-f8c370f7545f.png)