iotests: Test that qcow2's data-file is flushed

Flushing a qcow2 node must lead to the data-file node being flushed as
well.

Signed-off-by: Max Reitz <mreitz@redhat.com>
Reviewed-by: Andrey Shinkevich <andrey.shinkevich@virtuozzo.com>
Reviewed-by: Kevin Wolf <kwolf@redhat.com>
2 files changed