Without this, if the network goes down for a while, systemd will give up after 5 restarts:
Scheduled restart job, restart counter is at 5.
Stopped Nebula VPN service for myvpn.
nebula@myvpn.service: Start request repeated too quickly.
Failed with result 'exit-code'.
Failed to start Nebula VPN service for myvpn.
Most network services need this, but for VPNs it's extra important.