Store IUKs v2 in a dedicated directory (#15281)
At least in theory, there can very well be, for example, both IUKs v1 and v2 that upgrade from 4.1 to 4.3 and have the same filename. The difference will be the meaning of "from 4.1" and the content. Let's avoid having to deal with that.
config/chroot_local-includes/usr/src/iuk/t/data/webroot/tails/stable/iuk/Tails_s390x_0.11_to_0.12.1.iuk → config/chroot_local-includes/usr/src/iuk/t/data/webroot/tails/stable/iuk/v2/Tails_s390x_0.11_to_0.12.1.iuk