Add "Nvidia" option for the VNC role

Sometimes we need to work with the nvidia proprietary driver on remote machines that require a dedicated GPU.

For the Tesla 4 cards, we need the nvidia-tesla-460-driver package and this xorg.conf file:

Section "InputDevice"
    # generated from default
    Identifier     "Mouse0"
    Driver         "mouse"
    Option         "Protocol" "auto"
    Option         "Device" "/dev/psaux"
    Option         "Emulate3Buttons" "no"
    Option         "ZAxisMapping" "4 5"
EndSection

Section "InputDevice"
    # generated from default
    Identifier     "Keyboard0"
    Driver         "kbd"
EndSection

Section "Monitor"
    Identifier     "Monitor0"
    HorizSync      28.0-80.0
    VertRefresh    48.0-75.0
    Modeline       "1280x720_60.00" 74.48 1280 1336 1472 1664 720 721 724 746 -HSync +Vsync
    Option         "DPMS"
EndSection

Section "Device"
    Identifier     "Device0"
    Driver         "nvidia"
    VendorName     "NVIDIA Corporation"
    BusID          "PCI:0:5:0"
EndSection

Section "Screen"
    Identifier     "Screen0"
    Device         "Device0"
    Monitor        "Monitor0"
    DefaultDepth    24
    SubSection     "Display"
        Depth       24
        Virtual     1440 900 
    EndSubSection
EndSection

The cloud kernel also needs to be swapped for a regular kernel. See the jibri role for that, we're already doing it there.