cephfs: add validation for generic ephemeral volumes

This commit adds the validation of csi cephfs driver to work with
ephemeral volume support. With ephemeral volume support a user can
specify ephemeral volumes in its pod spec and tie the lifecycle
of the PVC with the POD.

An example POD spec looks like this:

```
kind: Pod
apiVersion: v1
metadata:
  name: csi-cephfs-demo-ephemeral-pod
spec:
  containers:
    - name: web-server
      image: docker.io/library/nginx:latest
      volumeMounts:
        - mountPath: /myspace
          name: mypvc
  volumes:
    - name: mypvc
      ephemeral:
        volumeClaimTemplate:
          spec:
            accessModes: [ ReadWriteOnce ]
            storageClassName: csi-cephfs-sc
            resources:
              requests:
                storage: 1Gi
```

Signed-off-by: Humble Chirammal <hchiramm@redhat.com>

e2e/cephfs.go

@@ -279,6 +279,7 @@ var _ = Describe("cephfs", func() {
 			appClonePath := cephFSExamplePath + "pod-restore.yaml"
 			appSmartClonePath := cephFSExamplePath + "pod-clone.yaml"
 			snapshotPath := cephFSExamplePath + "snapshot.yaml"
+			appEphemeralPath = cephFSExamplePath + "pod-ephemeral.yaml"
 
 			By("checking provisioner deployment is running", func() {
 				err := waitForDeploymentComplete(cephFSDeploymentName, cephCSINamespace, f.ClientSet, deployTimeout)
@@ -312,6 +313,28 @@ var _ = Describe("cephfs", func() {
 					}
 				})
 			}
+			By("verify generic ephemeral volume support", func() {
+				// snapshot beta is only supported from v1.17+
+				if !k8sVersionGreaterEquals(f.ClientSet, 1, 20) {
+					Skip("generic ephemeral volume only supported from v1.20+")
+				}
+				// create application
+				app, err := loadApp(appEphemeralPath)
+				if err != nil {
+					e2elog.Failf("failed to load application: %v", err)
+				}
+				app.Namespace = f.UniqueName
+				err = createApp(f.ClientSet, app, deployTimeout)
+				if err != nil {
+					e2elog.Failf("failed to create application: %v", err)
+				}
+				// delete pod
+				err = deletePod(app.Name, app.Namespace, f.ClientSet, deployTimeout)
+				if err != nil {
+					e2elog.Failf("failed to delete application: %v", err)
+				}
+				validateSubvolumeCount(f, 0, fileSystemName, subvolumegroup)
+			})
 
 			By("check static PVC", func() {
 				scPath := cephFSExamplePath + "secret.yaml"