the TTL should be lowered before the reboot. we should also use the
"standard" reboot procedure as per fabric so that we wait for the halt
to proceed.

the TTL procedure also now documents how the DNS changes can get
forcibly propagated.

finally, we merge the shutdown and migration stage as it seems like a
natural progression while keeping the number of steps constant from
before the TTL introduction.

by putting it on one line, we make the prompts work correctly.