wipefs will clear out the LUKS header very quickly which should render
the disk undecryptable, even with the master key. It's a good first
step that should work even on a running system.

This is basically ganeti, ipsec, iscsid, multipathd and timers, not
sure the latter actually works.

I had segfaults on nwipe on window resizes, hopefully that will help.

This is so i can add "installation" instructions after I figure out
how to rebuild fallax.

this allows us to move blockdev instances.

also retroactively update the limit in gnt-chi to reflect the actual
value there.

This way it can be split in multiple sections without getting in the
dreaded "heading level 4". We kept a cross-reference.