Error deleting snapshots

Issue

• We are receiving the message "Unable to delete volume " and "Unable to delete volume snapshot: " when we tried to delete them.
  These volumes were attached to the instances as /dev/vda and even though the instance is deleted the message is showed when we try to delete the volumes or snapshot. We were able to delete the volumes using the command cinder force-delete {volume-id} but we still can't delete the snapshots.

• From available data, it seems the cinder snapshot fails to remove as the volume/snapshot is missing from the backend storage(DellEQLSan).