getty-checktrust: Fix dependencies

It is not possible to use template units with directives, so

    Before=getty@.service

does not work.

There is a getty-pre.target unit which can be requested by services,
which want to be ordered before getty. Use that instead.

Although, WantedBy=getty@.service does work, this is strictly not
correct, because we want this service to run indepdendent from getty,
for example, to set the tag for lightdm. Change to
WantedBy=multi-user.target.

checktrust/getty-checktrust.service

@@ -1,10 +1,11 @@
 [Unit]
-Before=getty@.service
-
-[Install]
-WantedBy=getty@.service
+Wants=getty-pre.target
+Before=getty-pre.target
 
 [Service]
 Type=oneshot
 ExecStart=/usr/libexec/getty-checktrust
 RemainAfterExit=yes
+
+[Install]
+WantedBy=multi-user.target