Set NEXT_SNAPSHOT=1 for persistent images

[brodriguez-opennebula]

Description Next snapshot value on persistent VMs should be set to 1, because in case that the image used is not back chained by a regular template image, the first snapshot will have value 0 and will never be deleted

To Reproduce

• Create a persistent VM from a qcow image, not backed up by any other image
• Make a snapshot
  • This snapshot will have id 0
• Delete the snapshot
  • This will fail with code Cannot delete snapshot 0 for persistent disk images

Expected behavior The snapshot should be deleted. It does not get deleted because of Snapshots::test_delete controling the case (persistent && id == 0) and returns false

Details

• Affected Component: Core
• Hypervisor: detected on KVM
• Version: current

Additional context

Progress Status

• [ ] Code committed
• [ ] Testing - QA
• [ ] Documentation (Release notes - resolved issues, compatibility, known issues)