startup-tags: Pull startup-tags from sysinit.target

- Make startup-tags a dependency of sysinit-target

    WantedBy=sysinit.target

Note, that this creates a `Wanted` dependency in the target unit, which
implies an `After`-dependency as well (see systemd.target(5)).

- Disable default dependencies for this service unit, because service
  units have a default dependency on sysinit.target and we can't wait
  for ourelf.

    DefaultDependencies=no

- Wait for the root device remounted read/write, so that we can populate
  /node

    After=systemd-remount-fs.service

With this change, we no longer need to create an explicit dependency to
this unit in conditionally started service or socket units, because these units
have a default dependency on sysinit.target.

misc_systemd_units/startup-tags.service

@@ -1,7 +1,14 @@
 [Unit]
 
+DefaultDependencies=no
+After=systemd-remount-fs.service
+
 [Service]
+
 Type=oneshot
 RemainAfterExit=yes
 ExecStart=/usr/sbin/hostconfig --populate-node
 
+[Install]
+
+WantedBy=sysinit.target