iotests: fix 208 for luks format

Support luks images creatins like in 205
Signed-off-by: NVladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
Signed-off-by: NKevin Wolf <kwolf@redhat.com>

tests/qemu-iotests/208

@@ -28,7 +28,7 @@ with iotests.FilePath('disk.img') as disk_img_path, \
      iotests.VM() as vm:
 
     img_size = '10M'
-    iotests.qemu_img_pipe('create', '-f', iotests.imgfmt, disk_img_path, img_size)
+    iotests.qemu_img_create('-f', iotests.imgfmt, disk_img_path, img_size)
 
     iotests.log('Launching VM...')
     (vm.add_drive(disk_img_path, 'node-name=drive0-node', interface='none')