OSMC is systemd based, so you shouldn’t really be running a legacy LSB service script directly. It will work after a fashion but isn’t recommended.
Instead use the systemd service management commands such as:
sudo systemctl start vncboot.sevice
If you want to set the service to run at boot:
sudo systemctl enable vncboot.service
http://www.freedesktop.org/software/systemd/man/systemctl.html