Bug 6865 - Follow-up, Replace image-based gradient backgrounds with CSS3 gradients

Bug 6865 - Follow-up, Replace image-based gradient backgrounds with CSS3 gradients

Staff client login screen has a separate CSS file which wasn't
included in the original changes for Bug 6865. This caused a 404
error (missing background image).

Signed-off-by: Jared Camins-Esakov <jcamins@cpbibliography.com>
Tested in Chrome, FF, Safari, and IE8.

Signed-off-by: Paul Poulain <paul.poulain@biblibre.com>
(cherry picked from commit ac3b4061b7bb63b42cfbf8945789289215e90ee4)

Signed-off-by: Chris Nighswonger <chris.nighswonger@gmail.com>