journalctl: consider shut down namespaced sd-journald instance synced

journalctl: consider shut down namespaced sd-journald instance synced

If the namespaced systemd-journald instance was shut down due to
inactivity, we can consider it synchronized, so avoid throwing an error
in such case.

This should help with the random TEST-44-LOG-NAMESPACE fails where we
might try to sync the namespace just after it was shut down:

[    7.682941] H testsuite-44.sh[381]: + systemd-run --wait -p LogNamespace=foobaz echo 'hello world'
[    7.693916] H systemd-journald[389]: Failed to open /dev/kmsg, ignoring: Operation not permitted
[    7.693983] H systemd-journald[389]: Collecting audit messages is disabled.
[    7.725511] H systemd[1]: Started systemd-journald@foobar.service.
[    7.726496] H systemd[1]: Listening on systemd-journald-varlink@foobaz.socket.
[    7.726808] H systemd[1]: Listening on systemd-journald@foobaz.socket.
[    7.750774] H systemd[1]: Started run-u3.service.
[    7.795122] H systemd[1]: run-u3.service: Deactivated successfully.
[    7.842042] H testsuite-44.sh[390]: Running as unit: run-u3.service; invocation ID: 56380adeb36940a8a170d9ffd2e1e433
[    7.842561] H systemd[1]: systemd-journald-varlink@foobaz.socket: Deactivated successfully.
[    7.842762] H systemd[1]: Closed systemd-journald-varlink@foobaz.socket.
[    7.846394] H systemd[1]: systemd-journald@foobaz.socket: Deactivated successfully.
[    7.846566] H systemd[1]: Closed systemd-journald@foobaz.socket.
[    7.852983] H testsuite-44.sh[390]: Finished with result: success
[    7.852983] H testsuite-44.sh[390]: Main processes terminated with: code=exited/status=0
[    7.852983] H testsuite-44.sh[390]: Service runtime: 44ms
[    7.852983] H testsuite-44.sh[390]: CPU time consumed: 8ms
[    7.852983] H testsuite-44.sh[390]: Memory peak: 880.0K
[    7.852983] H testsuite-44.sh[390]: Memory swap peak: 0B
[    7.853785] H testsuite-44.sh[381]: + journalctl --namespace=foobar --sync
[    7.860095] H systemd-journald[389]: Received client request to sync journal.
[    7.862119] H testsuite-44.sh[381]: + journalctl --namespace=foobaz --sync
[    7.868381] H journalctl[396]: Failed to connect to /run/systemd/journal.foobaz/io.systemd.journal: Connection refused
[    7.871498] H systemd[1]: testsuite-44.service: Main process exited, code=exited, status=1/FAILURE
[    7.871642] H systemd[1]: testsuite-44.service: Failed with result 'exit-code'.
[    7.930772] H systemd[1]: Failed to start testsuite-44.service.