Dropdown in panel header does not inherit its colors

Fix for issue #10627.

I tested on a Mac using browsers:
* Firefox 23.0.1
* Safari 6.0.5
* Chrome 29.0.1547.62
* Opera 11.61

I am new to bootstrap and probably my approach is different than what it is expected.
For example, I am inheriting the text color from panel, but maybe I should use the link color.
I will try to be more familiar with bootstrap. Please let me know if I need todo any changes.