mkfs.ubifs: Clear direct_write property when closing target
Direct writing is not allowd on an UBI volume, unless the volume is set
with direct_write property. The open_target sets direct_write property,
don't forget to clear direct_write property for UBI volume when closing
target.
Fixes: a48340c335dab ("mkfs.ubifs: use libubi to format UBI volume") Signed-off-by: Zhihao Cheng <chengzhihao1@huawei.com> Signed-off-by: David Oberhollenzer <david.oberhollenzer@sigma-star.at>