package nvidia-331-updates overwrites nouveau configuration

[Peter Hurley]

Dec 11 2014 updates included nvidia-331-updates and associated packages (like nvidia-prime).

I don't use the binary driver, so this blew away my working nouveau configuration and xorg.conf (which I had to restore from backup).

Also, DKMS failed to build the nvidia module because I'm running custom kernels (latest mainline or linux-next plus whatever my current patch stack is before upstreaming them). The install should test for these error conditions and revert configuration changes, rather than leaving a broken boot.