VR HealthCheck fails when there are no VMs deployed

### problem

A VR HA pair or single VR report the health check as failed when there are no VMs deployed to that VR. This causes alerts in the logs, triggering investigations.

Under the VR health check:
"dhcp_check.py" reports "No VMs running data available, skipping" (which is good)
"webserver.service" reports "warning" "service down at last check xxxxxxx" (which is bad)

This issue goes away if a VM is deployed and returns if it is deleted. If there is an VR HA pair, the failure report bounces back and forth between the 2 VR in the HA pair.

The attached screenshot has r-517/r518 in an HA pair as well as r-519/r-520.

### versions

This is on CloudStack 4.22.

### The steps to reproduce the bug

1. Create a VR Router (HA or not) and an isolated network
2. Deploy a VM to that isolated network
3. Delete the VM
4. The next health check will then report as failed

### What to do about it?

The VR healthcheck should not fail if there are no VMs deployed.

Commencez par dhcp_check.py et le chemin de health-check de webserver.service, puis reproduisez le problème sur un VR avec un réseau isolé après avoir supprimé sa VM. Le travail est terminé lorsqu’un VR sans VMs déployées reste sain et n’émet pas l’alerte de failure signalée, y compris pour une paire HA.

Rédigé par le modèle d'indexation à partir du texte de l'issue.