Fixed UI issue with scheduled maint periods on the check page.

Fixes https://github.com/flpjck/flapjack/issues/427.

![screenshot 2014-01-28 14 29 43](https://f.cloud.github.com/assets/1730965/2024587/b86ffaa4-886b-11e3-9af8-99cea2e64527.png)