Description of problem:
KubePersistentVolumeFillingUp is firing for Filesystem PVCs that hold a VM disk although them being filled is by design

Version-Release number of selected component (if applicable):
4.10.0

How reproducible:
100%

Steps to Reproduce:
1. Create DV, VM (manifests below)
2. Observe alerts

Actual results:
KubePersistentVolumeFillingUp firing

Expected results:
KubePersistentVolumeFillingUp not firing

Additional info:
We can now use the following label on PVCs to prevent the alert from going off:
alerts.k8s.io/KubePersistentVolumeFillingUp: disabled

Manifests:
apiVersion: cdi.kubevirt.io/v1beta1
kind: DataVolume
metadata:
  name: simple-dv-cephfs
spec:
  source:
      http:
         url: "http://.../Fedora-Cloud-Base-34-1.2.x86_64.qcow2"
  pvc:
    storageClassName: ocs-storagecluster-cephfs
    volumeMode: Filesystem
    accessModes:
    - ReadWriteOnce
    resources:
      requests:
        storage: 5Gi
---
apiVersion: kubevirt.io/v1
kind: VirtualMachine
metadata:
  name: simple-vm
  namespace: default
spec:
  running: true
  template:
    metadata:
      labels: {kubevirt.io/domain: simple-vm,
        kubevirt.io/vm: simple-vm}
    spec:
      domain:
        devices:
          disks:
          - disk: {bus: virtio}
            name: dv-disk
          - disk: {bus: virtio}
            name: cloudinitdisk
        resources:
          requests: {memory: 2048M}
      volumes:
      - dataVolume: {name: simple-dv-cephfs}
        name: dv-disk
      - cloudInitNoCloud:
          userData: |
            #cloud-config
            password: fedora
            chpasswd: { expire: False }
        name: cloudinitdisk