Shrink the search label in Manage User page

Before:
![screen shot 2014-11-01 at 10 51 54 pm](https://cloud.githubusercontent.com/assets/1354889/4963367/1ecae5a8-670e-11e4-9d22-141327b2e334.png)

After:
![screen shot 2014-11-01 at 10 52 06 pm](https://cloud.githubusercontent.com/assets/1354889/4963366/1c0a9408-670e-11e4-9672-107c2ae7a264.png)


Fixes #17815
!important can be abused thus the generalization around not to use it. As anything, there is a right way and wrong way. In this particular case, the !important is used to override a the default label style for a specific case. That's one good way of using it. 

For more details see: http://css-tricks.com/when-using-important-is-the-right-choice/