Test what happens when the Pods for an IngressBackend are scaled to 0 (and fix if necessary)
I suspect that in this case, probes will be defined for the backends in the generated VCL, but they are unused, since the backends will not be defined. That would lead to invalid VCL (probe defined but not used).
If so, we'll need to add a condition in the VCL template to the effect that the probe definition for a Service $svc
is only generated if len($svc.Addresses) > 0
.