Problems with fatal signal delivery

[cole-miller]

Since the fix #119, we've seen this tar invocation complaining about the data directory changing while archiving is in progress:

jepsen.dqlite/src/jepsen/dqlite/db.clj

Line 274 in c9a178a

(c/exec :sudo :tar :cjf tarball data-dir)

And in this Jepsen run, it seems that a running raft instance observes its data directory in a bizarre state that might be caused by Jepsen finalization:

https://github.com/canonical/jepsen.dqlite/actions/runs/5853720376/job/15875114455

Need to investigate whether/why raft shutdown is not happening in an orderly way.