Storing the SCION path sqlite databases persistently on disk is a valid
setup that improves performance, but may have outstanding bugs that need
to be investigated, so this makes persisent storage optional, off by
default.
It was wrong to use StateDirectory to keep the scion-control and
scion-router runtime databases on disk for the next run. I observed that
doing this means a reboot, or power outage can corrupt the temporary
runtime databases for the next service start, leading scion ping and
other functionality to stop working permanently, since those files are
not managed in an atomic manner by the golang code.
these changes were generated with nixq 0.0.2, by running
nixq ">> lib.mdDoc[remove] Argument[keep]" --batchmode nixos/**.nix
nixq ">> mdDoc[remove] Argument[keep]" --batchmode nixos/**.nix
nixq ">> Inherit >> mdDoc[remove]" --batchmode nixos/**.nix
two mentions of the mdDoc function remain in nixos/, both of which
are inside of comments.
Since lib.mdDoc is already defined as just id, this commit is a no-op as
far as Nix (and the built manual) is concerned.
