units: restore Before dependencies for systemd-vconsole-setup.service

units: restore Before dependencies for systemd-vconsole-setup.service

When the service is run in the initramfs, it is possible for it to get started
and not be fast enough to exit before the root switch happens. It is started
multiple times (depending on the consoles being detected), and runs
asynchronously, so this is quite likely. It'll then get killed by killall(),
and systemd will consider the service failed. To avoid all this, just wait
for the service to terminate on it's own.

Before=initrd-switch-root.target should be good for the initramfs, and
Before=shutdown.tuarget should be good for the real system, although it's
unlikely to make any difference there.