Bug#274486: preseed: looks need to rewrite debconf/frontend before reboot
When I tried d-i with my debconf seed, 1st stage is OK, but 2nd stage
goes infinite loop because Newt frontend can't be found.
d-i 1st stage uses newt fronend by default, so debconf seed file
d-i debconf/frontend string newt
But 2nd stage hasn't this forntend, has 'Dialog' instead of it.
IMHO preseed or base-config should rewrite this variable.