e2e: Add E2E to mount rbd PVC as ro in app

Added an E2E to mount rbd PVC as readonly
in application pod and try to create some
file in Readonly PVC,when we try to create
files on RO PVC, we should get error.

Signed-off-by: Madhu Rajanna <madhupr007@gmail.com>

e2e/rbd.go

@@ -720,6 +720,50 @@ var _ = Describe("RBD", func() {
 				}
 			})
 
+			By("Mount pvc as readonly in pod", func() {
+				// create pvc and bind it to an app
+				pvc, err := loadPVC(pvcPath)
+				if err != nil {
+					Fail(err.Error())
+				}
+
+				pvc.Namespace = f.UniqueName
+
+				app, err := loadApp(appPath)
+				if err != nil {
+					Fail(err.Error())
+				}
+
+				app.Namespace = f.UniqueName
+				label := map[string]string{
+					"app": app.Name,
+				}
+				app.Labels = label
+				app.Spec.Volumes[0].PersistentVolumeClaim.ClaimName = pvc.Name
+				app.Spec.Volumes[0].PersistentVolumeClaim.ReadOnly = true
+				err = createPVCAndApp("", f, pvc, app, deployTimeout)
+				if err != nil {
+					Fail(err.Error())
+				}
+
+				opt := metav1.ListOptions{
+					LabelSelector: fmt.Sprintf("app=%s", app.Name),
+				}
+
+				filePath := app.Spec.Containers[0].VolumeMounts[0].MountPath + "/test"
+				_, stdErr := execCommandInPodAndAllowFail(f, fmt.Sprintf("echo 'Hello World' > %s", filePath), app.Namespace, &opt)
+				readOnlyErr := fmt.Sprintf("cannot create %s: Read-only file system", filePath)
+				if !strings.Contains(stdErr, readOnlyErr) {
+					Fail(stdErr)
+				}
+
+				// delete pvc and app
+				err = deletePVCAndApp("", f, pvc, app)
+				if err != nil {
+					Fail(err.Error())
+				}
+			})
+
 			// Make sure this should be last testcase in this file, because
 			// it deletes pool
 			By("Create a PVC and Delete PVC when backend pool deleted", func() {