vfs_zfsacl: return synthesized ACL when ZFS return ENOTSUP

vfs_zfsacl: return synthesized ACL when ZFS return ENOTSUP

This allows accessing the ZFS .snapshots directory where ZFS returns
ENOTSUP when calling acl(".snapshots").

Bug: https://bugzilla.samba.org/show_bug.cgi?id=13175

Signed-off-by: Ralph Boehme <slow@samba.org>
Reviewed-by: Jeremy Allison <jra@samba.org>
Autobuild-User(master): Jeremy Allison <jra@samba.org>
Autobuild-Date(master): Fri May 18 22:03:21 CEST 2018 on sn-devel-144

(cherry picked from commit f93cc232377d4c686ac35ee5e14e798974bc0700)

Autobuild-User(v4-8-test): Karolin Seeger <kseeger@samba.org>
Autobuild-Date(v4-8-test): Wed Nov 28 13:20:55 CET 2018 on sn-devel-144