[#27111] Maintenance page breaks installation process.

Screenshot of initial /install.php page before this PR:
![screen shot 2014-11-10 at 4 55 31 pm](https://cloud.githubusercontent.com/assets/33429/4973230/fed99338-68b7-11e4-9581-2d2d6cc2fbea.png)

Screenshot of initial /install.php page after this PR:
![screen shot 2014-11-10 at 4 54 48 pm](https://cloud.githubusercontent.com/assets/33429/4973234/0e1d41b4-68b8-11e4-911a-ff72d493a7c2.png)