systemd: run After update_engine
systemd: run After update_engine

d01a4c35547df8affb025840f02caa3ab209e9be dropped a Requires/After on
update-engine.service, since those would prevent systemd from restarting
locksmithd if update-engine failed. However, that change created a
race in which locksmithd would start before update_engine, fail with

    Cannot get update engine status: The name com.coreos.update1 was not provided by any .service files

and be restarted by systemd 10 seconds later.

Ideally update_engine would support bus activation, but enabling that
would require users to take an additional step when disabling
update_engine, breaking backward compatibility. Instead, add an After
to fix the race, but do not pull in update_engine. In principle we
could also add a Wants, but that would change behavior in a corner case
(restarting locksmithd with update_engine stopped).

coreos/locksmith,coreos/locksmith