iotests: Add preallocated growth test for qcow2

Signed-off-by: Max Reitz <mreitz@redhat.com>
Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>
Message-id: 20170613202107.10125-17-mreitz@redhat.com
Signed-off-by: Max Reitz <mreitz@redhat.com>
3 files changed