* daemon/zero.c (do_zero): Detect write and close errors.

Nearly every file-related function in daemons/*.c is affected:
Remove this pair of statements from each affected do_* function:
-  NEED_ROOT (return -1);
-  ABS_PATH (dir, return -1);
and change the type of the corresponding parameter to "const char *".
* src/generator.ml: Emit NEED_ROOT just once, even when there are two or
more Pathname args.

Then update each affected function, removing each uses of RESOLVE_DEVICE,
now that it's generated in caller from stub.c.
* daemon/blockdev.c (call_blockdev): Remove use of RESOLVE_DEVICE.
* daemon/devsparts.c (do_mkfs): Likewise.
* daemon/ext2.c (do_e2fsck_f, do_get_e2label, do_get_e2uuid): Likewise.
(do_resize2fs, do_set_e2label, do_set_e2uuid, do_tune2fs_l): Likewise.
* daemon/fsck.c (do_fsck): Likewise.
* daemon/grub.c (do_grub_install): Likewise.
* daemon/lvm.c (do_lvremove, do_pvcreate, do_pvremove): Likewise.
(do_pvresize): Likewise.
* daemon/mount.c (do_mount_vfs): Likewise.
* daemon/ntfs.c (do_ntfs_3g_probe): Likewise.
* daemon/scrub.c (do_scrub_device): Likewise.
* daemon/sfdisk.c (sfdisk, sfdisk_flag): Likewise.
* daemon/swap.c (do_mkswap, do_mkswap_L, do_mkswap_U): Likewise.
(do_swapoff_device, do_swapon_device): Likewise.
* daemon/zero.c (do_zero): Likewise.
* daemon/zerofree.c (do_zerofree): Likewise.

Use this command:
  git grep -l -w IS_DEVICE|xargs perl -pi -e \
    's/\b(?:IS_DEVICE)\b( \(.*?,) (.*?)\)/RESOLVE_DEVICE$1 return $2)/'