Add workaround for Ubuntu postinstall script bug?

[bcdarwin]

I'm currently running into this longstanding issue on Ubuntu 20.04 with the following configuration:

  - role: nvidia.nvidia_driver
    nvidia_driver_ubuntu_branch: 340
    nvidia_driver_ubuntu_packages: [ 'nvidia-340' ]

I don't have this issue on machines when using the default NVIDIA 450 packages but I can't install this on all my systems due to hardware compatibility, and anyway it's possible that some recent versions are affected in combination with some kernels anyway (e.g., in the Launchpad thread above, a user reports having issues with version 465).

It seems there is known error text and a known workaround, so it might be useful to add to this role.