zfs posix default permissions lost on reboot or unmount

[SRU Justification][XENIAL]
Commit 4967a3e introduced a typo that caused the ZPL to store the
intended default ACL as an access ACL. Due to caching this problem
may not become visible until the filesystem is remounted or the inode
is evicted from the cache.

[FIX]
https://github.com/zfsonlinux/zfs/commit/98f03691a4c08f38ca4538c468e9523f8e6b24be

[TESTCASE]
from https://github.com/zfsonlinux/zfs/issues/4520:

[root@localhost ~]# cd /mnt/data/
[root@localhost data]# mkdir test_dir
[root@localhost data]# setfacl -R --mask -m u:uadm:rwX test_dir/
[root@localhost data]# setfacl -R -d --mask -m u:uadm:rwX test_dir/
[root@localhost data]# getfacl test_dir/
# file: test_dir/
# owner: root
# group: root
user::rwx
user:uadm:rwx
group::r-x
mask::rwx
other::r-x
default:user::rwx
default:user:uadm:rwx
default:group::r-x
default:mask::rwx
default:other::r-x

[root@localhost data]# reboot

After a reboot without the fix one gets the following ACLs:

[root@localhost ~]# cd /mnt/data/
[root@localhost data]# getfacl test_dir/
# file: test_dir/
# owner: root
# group: root
user::rwx
user:uadm:rwx
group::r-x
mask::rwx
other::r-x

With the fix:

[root@localhost data]# getfacl test_dir/
# file: test_dir/
# owner: root
# group: root
user::rwx
user:uadm:rwx
group::r-x
mask::rwx
other::r-x
default:user::rwx
default:user:uadm:rwx
default:group::r-x
default:mask::rwx
default:other::r-x

[REGRESSION POTENTAL]
Minimal ZFS only and touches just acl setting. This corrects just the ACL_TYPE_DEFAULT case for the ACL setting for ZFS, and sets it to the *correct* name. It is a trivial one line fix.

----------------------------------------------

Ubuntu 16.04 server

Problem: Posix default permissions on zfs datasets are lost after rebooting the server or unmounting/remount.

See here for details and fix: https://github.com/zfsonlinux/zfs/issues/4520

---
AlsaDevices:
 total 0
 crw-rw----+ 1 root audio 116, 1 Apr 24 22:44 seq
 crw-rw----+ 1 root audio 116, 33 Apr 24 22:44 timer
AplayDevices: Error: [Errno 2] No such file or directory
ApportVersion: 2.20.1-0ubuntu2
Architecture: amd64
ArecordDevices: Error: [Errno 2] No such file or directory
AudioDevicesInUse: Error: command ['fuser', '-v', '/dev/snd/seq', '/dev/snd/timer'] failed with exit code 1:
DistroRelease: Ubuntu 16.04
HibernationDevice: RESUME=/dev/mapper/ubuntu--vg-swap_1
IwConfig: Error: [Errno 2] No such file or directory
MachineType: To be filled by O.E.M. To be filled by O.E.M.
NonfreeKernelModules: zfs zunicode zcommon znvpair zavl
Package: linux (not installed)
PciMultimedia:

ProcEnviron:
 TERM=xterm-256color
 PATH=(custom, no user)
 LANG=en_US.UTF-8
 SHELL=/bin/bash
ProcFB:
 0 nouveaufb
 1 astdrmfb
ProcKernelCmdLine: BOOT_IMAGE=/vmlinuz-4.4.0-21-generic root=/dev/mapper/hostname--vg-root ro
ProcVersionSignature: Ubuntu 4.4.0-21.37-generic 4.4.6
RelatedPackageVersions:
 linux-restricted-modules-4.4.0-21-generic N/A
 linux-backports-modules-4.4.0-21-generic N/A
 linux-firmware 1.157
RfKill: Error: [Errno 2] No such file or directory
Tags: xenial
Uname: Linux 4.4.0-21-generic x86_64
UpgradeStatus: No upgrade log present (probably fresh install)
UserGroups:

_MarkForUpload: True
dmi.bios.date: 07/23/2013
dmi.bios.vendor: American Megatrends Inc.
dmi.bios.version: 6702
dmi.board.asset.tag: To be filled by O.E.M.
dmi.board.name: P8B-X series
dmi.board.vendor: ASUSTeK Computer INC.
dmi.chassis.asset.tag: To Be Filled By O.E.M.
dmi.chassis.type: 17
dmi.chassis.vendor: To Be Filled By O.E.M.
dmi.chassis.version: To Be Filled By O.E.M.
dmi.modalias: dmi:bvnAmericanMegatrendsInc.:bvr6702:bd07/23/2013:svnTobefilledbyO.E.M.:pnTobefilledbyO.E.M.:pvrTobefilledbyO.E.M.:rvnASUSTeKComputerINC.:rnP8B-Xseries:rvr:cvnToBeFilledByO.E.M.:ct17:cvrToBeFilledByO.E.M.:
dmi.product.name: To be filled by O.E.M.
dmi.product.version: To be filled by O.E.M.
dmi.sys.vendor: To be filled by O.E.M.