Non-functional change: Add commented-out nomodeset argument

Including the `nomodeset` into the Ubuntu and Debian tasks is an obscure
setting. This includes that option commented out. About `nomodeset`, from
http://ubuntuforums.org/showthread.php?t=1613132:

The newest kernels have moved the video mode setting into the kernel. So all
the programming of the hardware specific clock rates and registers on the video
card happen in the kernel rather than in the X driver when the X server
starts.. This makes it possible to have high resolution nice looking splash
(boot) screens and flicker free transitions from boot splash to login screen.
Unfortunately, on some cards this doesnt work properly and you end up with a
black screen. Adding the nomodeset parameter instructs the kernel to not load
video drivers and use BIOS modes instead until X is loaded.