overlay-setup: Run before several /var using units

Systemd ships several units that require access to /var but are not
ordered after local-fs.target. It would be better if they did, but
that's not the case today. Systemd doesn't expect the kind of mount
post-processing that's done here, so order the unit before all of those
units.

https://phabricator.endlessm.com/T35323

eos-live-boot-overlayfs-setup.service

@@ -2,9 +2,30 @@
 Description=Endless live boot overlayfs setup
 DefaultDependencies=no
 After=ostree-remount.service var.mount
-Before=local-fs.target systemd-random-seed.service
+Before=local-fs.target
 ConditionKernelCommandLine=endless.live_boot
 
+# Systemd ships several units that require access to /var but are not ordered
+# after local-fs.target. It would be better if they did, but that's not the
+# case today. Systemd doesn't expect the kind of mount post-processing that's
+# done here.
+#
+# You can find these with the following command:
+#
+# grep -rl -e StateDirectory -e CacheDirectory -e LogsDirectory -e var.mount \
+#   -e 'RequiresMountsFor=.*/var' /usr/lib/systemd/system \
+#   | xargs grep -l -e DefaultDependencies | sort
+Before[email protected]
+Before[email protected]
+Before=systemd-journal-flush.service
+Before=systemd-pstore.service
+Before=systemd-random-seed.service
+Before=systemd-rfkill.service
+Before=systemd-rfkill.socket
+Before=systemd-timesyncd.service
+Before=systemd-update-utmp-runlevel.service
+Before=systemd-update-utmp.service
+
 [Service]
 Type=oneshot
 ExecStart=/usr/sbin/eos-live-boot-overlayfs-setup