Normally anaconda uses grubby to update bootloader configuration. But
unfortunately it breaks grub configuration (removes trailing "=", so
empty variable assignment xen_rm_opts= is broken). Instead of reworking
the whole bootloader support in anaconda, just regenerate grub.cfg at
the end.
InstallClass.postAction isn't called from anywhere, move things to
anaconda post-scripts. Add regenerate of initramfs image to include
qubes-pciback module.