`swarm-bao-pki` was a `RemainAfterExit` oneshot. Once active, nothing
re-ran it: a switch restarts it only when its definition changes, and a
`Requires=`/`Wants=` on an active unit is satisfied without running it.
On muede-lpt2 the 10:57Z switch that added the builder line did change
the unit, so switch-to-configuration stopped it in its stop phase. A
start of `container@swarm-bao` 4 s later (before the daemon-reload at
10:57:35Z) pulled it back in through `swarm-bao-certs` with the OLD
definition, which had no builder line: 48 ms, nothing missing. The start
phase then found it active and did nothing. The 20:14Z switch that
enabled the builder left the unit unchanged, so it was never re-run, and
`container@swarm-builder` crash-looped on the absent `builder.pem`.
The unit now goes inactive after each run. Every switch starts
`multi-user.target`, which runs it again post-reload with the current
definition, and every unit that wants or requires it runs it on its own
start. Each line is idempotent on presence, so an existing leaf is never
re-signed.
The three consumers started from `machines.target` rather than
`multi-user.target` also want it, since `After=` alone does not order
against a job in another transaction: the builder's and the review
classifier's containers (nspawn `--load-credential`) and
`swarm-nats-auth-secrets` (pulled in by the queue's container).
Fixes#5284
b5053d9a80