motd: unbreak for source upgrade

In case of source upgrade path from 12.x proper merge of new /etc
installs /etc/motd.template. Becase of that, the system in left
without symlink /etc/motd -> /var/run/motd but with stale /etc/motd contents.

Fix it creating symlink despite of presence of /etc/motd.template.

MFC after: 1 week