Feature #8415: Migrate from aufs to overlayfs
Make memory erasure feature compatible with overlayfs
The "Erasure of the overlayfs read-write branch on shutdown" test scenario fails. But interestingly, "Tails erases memory on DVD boot medium removal: overlayfs read-write branch" passes. Looks like
live-boot behaves slightly differently on overlayfs than on aufs, which seems to explain why mountpoints are not visible and can't be unmounted and thus cleaned.
I don't think it's worth spending time on this before #15477 is done: perhaps the revamping of how mountpoints are managed by live-boot will fix this problem, perhaps it'll make it harder to solve, but in any case better do the overlayfs-specific work only once, after that other migration is done.