Bug#898391: nvidia-driver-libs-nonglvnd: cannot upgrade due to libglvnd0 conflict

[Tom Maneiro]

I'm also affected here: I'm trying to update to Mesa 17.3 after 
installing the 390.48.2~bpo9+3 drivers on my Stretch laptop (I'm using a 
hybrid graphics laptop so I need both drivers for my setup), but either 
I get updated Mesa or lose the nVidia blob due to conflicts with the new 
packaging specs (??), rendering my setup completely unupgradable and 
unusable.