dhcp: T3180: bugfix NameError when slicing server ranges
dhcp: T3180: bugfix NameError when slicing server ranges

Introduced in commit e46def834483e ("dhcp: T3100: re-add range slicing support
when exclude addresses are used") by not obeying the move from list to dict
and still relying on the old list names variables.

vyos/vyos-1x,vyos/vyos-1x,vyos/vyos-1x,vyos/vyos-1x