Consider switching back to Debian sid's aufs-dkms
It now supports Linux 4.15. I think this time I want to keep the upstream submodule + the code that builds it and introduce a config variable that toggles it on/off so we can always prepare a branch with a new kernel without waiting for aufs-dkms in Debian to catch up.
- Blocked by #15320 (closed)
- Blocks tails/accounting#15334