Update to read subpath from volume handle

[leakingtapan]

Is this a bug fix or adding new feature?
Update to read subpath from volume handle
Fixes: #100

Tested manually with following specs and verified it works:

---

kind: StorageClass
apiVersion: storage.k8s.io/v1
metadata:
  name: efs-sc
provisioner: efs.csi.aws.com

---
apiVersion: v1
kind: PersistentVolume
metadata:
  name: efs-pv1
spec:
  capacity:
    storage: 5Gi
  volumeMode: Filesystem
  accessModes:
    - ReadWriteMany
  persistentVolumeReclaimPolicy: Retain
  storageClassName: efs-sc
  csi:
    driver: efs.csi.aws.com
    volumeHandle: fs-0ec5418f:/test1

---
apiVersion: v1
kind: PersistentVolumeClaim
metadata:
  name: efs-claim1
spec:
  accessModes:
    - ReadWriteMany
  storageClassName: efs-sc
  resources:
    requests:
      storage: 5Gi
---

apiVersion: v1
kind: PersistentVolume
metadata:
  name: efs-pv2
spec:
  capacity:
    storage: 5Gi
  volumeMode: Filesystem
  accessModes:
    - ReadWriteMany
  persistentVolumeReclaimPolicy: Retain
  storageClassName: efs-sc
  csi:
    driver: efs.csi.aws.com
    volumeHandle: fs-0ec5418f:/test2

---
apiVersion: v1
kind: PersistentVolumeClaim
metadata:
  name: efs-claim2
spec:
  accessModes:
    - ReadWriteMany
  storageClassName: efs-sc
  resources:
    requests:
      storage: 5Gi

---
apiVersion: v1
kind: Pod
metadata:
  name: efs-app
spec:
  containers:
  - name: app
    image: centos
    command: ["/bin/sh"]
    args: ["-c", "while true; do echo $(date -u) >> /data/out.txt; sleep 5; done"]
    volumeMounts:
    - name: pv1
      mountPath: /data/pv1
    - name: pv2
      mountPath: /data/pv2
  volumes:
  - name: pv1
    persistentVolumeClaim:
      claimName: efs-claim1
  - name: pv2
    persistentVolumeClaim:
      claimName: efs-claim2

[leakingtapan]

/hold

[k8s-ci-robot]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: leakingtapan

The full list of commands accepted by this bot can be found here.

The pull request process is described here

Needs approval from an approver in each of these files:

• OWNERS [leakingtapan]

Approvers can indicate their approval by writing /approve in a comment
Approvers can cancel approval by writing /approve cancel in a comment

[skang0601]

Any progress on this issue?

[leakingtapan]

@skang0601 thx for the follow up. I still need to add some unit tests for the new code added. After coverage is back up, you should be good to go