We already had it on the socket units, so it's possible that
systemd-journald.service would be stopped and then restarted when trafic hits
the sockets when something logs. Let's not try to stop it. It is supposed to
run until the end and be eventually killed in the final killing spree.
This might (or not) help with #23287.
To make things simple and robust when debugging journald, we'll leave
the SO_TIMESTAMP invocations in the C code in place, even if they are
now typically redundant, given that the sockets are already passed into
the process with SO_TIMESTAMP turned on now.
