change the default screensaver from black to ubuntu logo

We need to change the default screensaver. The problem with the current screensaver is that the first time you meet it is when the screen suddenly turns black during the installation. That is very confusing for most users, as the first thought always is that the installation has crashed.

I suggest a screensaver that helps brand Ubuntu, like for example the "Floating Ubuntu" screensaver. It could also be a textbased screensaver that could run on older machines witch doesn't support 3D.