Fix the boxgrinder appliance postinstall

Spent an entire day tracking down a broken libguestfs. Finally established that
the virtio_console.ko kernel module was missing, due to a missing dependency
from libguestfs on linux-image-extra-virtual.
Comment out per-provider customizations for now

These don't yet work thanks to ongoing issues with libguestfs, so temporarily
reinstate the obvious way of installing the VMware tools.