VolumeSnapshotContents are accumulated during backup

Description of problem:

Ceph limit is 100 VolumeSnapshots per PVC.

While running CSI backup for a long period, it can fail.  

tested 2 flows:
1. backup with 'deletionPolicy'  set to Delete

2. delete backup using Velero

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

How reproducible:

OCP-4.11.0

OADP-1.1.0-74

Steps to Reproduce:

• Running CSI backup for a long period

1.  'deletionPolicy'  set to Delete

  - VolumeSnapshotContent create with 'Delete' policy during backup  

  - When the backup is finished, VolumeSnapshotContent delete
  - New VolumeSnapshotContents are created with 'Retain' and size=0

2. Delete backup using Velero

  - backup plan delete
  - backup delete from the bucket
  - VolumeSnapshotContent not delete

Actual results:

VolumeSnapshotContents are accumulated and backup can be failed (long period test)

Expected results:

1. VolumeSnapshotContents should not be created after the backup finished

2. Velero backup delete {Name} should delete the VolumeSnapshotContents

Additional info:

Restore works OK

Test Steps:

1. VolumeSnapshotClass 'deletionPolicy'  set to Delete
2. Running CSI backup of 1ns with 50 pods 
3. During the backup, PVC created with 'Delete' policy and 'restore size > 0'
4. Right after the backup done (5min duration) , the "VolumeSnapshotContent" were deleted but new were created with 'Retain' policy and 'restore size = 0'
5. Running restore - finished successfully

http://pastebin.test.redhat.com/1073064