sheepdog: add missing .bdrv_has_zero_init

sheepdog: add missing .bdrv_has_zero_init

Commit 3ac21627 changed the behaviour of bdrv_has_zero_init() to default
to 0. In the review for Sheepdog it turned out that enabling it is safe,
so that commit updated one BlockDriver definition of sheepdog to use
bdrv_has_zero_init_1, missed however that there are more BlockDrivers in
the driver. Fix these now.

Cc: Kevin Wolf <[email protected]>
Cc: Stefan Hajnoczi <[email protected]>
Signed-off-by: Liu Yuan <[email protected]>
Reviewed-by: MORITA Kazutaka <[email protected]>
Signed-off-by: Kevin Wolf <[email protected]>