Support Volume Snapshot

Ref: https://github.com/harvester/harvester/issues/2294

Verify Steps:

1. Install Harvester with any nodes
2. Create an Image for VM creation
3. Create vm1 with the image and an additional data volume disk-1
4. Login to vm1, execute following commands:
   • fdisk /dev/vdb with new and primary partition
   • mkfs.ext4 /dev/vdb1
   • mkdir vdb && mount -t ext4 /dev/vdb1 vdb
   • ping 127.0.0.1 | tee -a vdb/test
5. Navigate to Volumes, then click Take Snapshot button on disk-1 of vm1 into vm1-disk-2
6. Navigate to Virtual Machines, then update vm1 to add existing volume vm1-disk-2
7. Login to vm1 then mount /dev/vdb1(disk-1) and /dev/vdc1(disk-2) into vdb and vdc
8. test file should be appeared in both folders of vdb and vdc
9. test file should not be empty in both folders of vdb and vdc