@lgg you are using systemd so, If you need any other service to be executed before kamailio you need to override the systemd unit file with the needed services.
Take a look over https://www.freedesktop.org/software/systemd/man/systemd.unit.html#Examples or https://wiki.archlinux.org/index.php/Systemd#Editing_provided_units as a guide.
Not a kamailio code bug, closing