caddy-frontend: Add missing promise on each exposed node

Each node requests a frontend to publish information about itself, and it shall
wait for the frontend to be available.
1 job for fix/caddy-frontend-statstic-node-promise in 0 seconds
Status Job ID Name Coverage
  External
failed SlapOS.SoftwareReleases.IntegrationTest-luke/fix/caddy-frontend-statstic-node-promise

02:47:20