vfs_acl_common: avoid setting POSIX ACLs if "ignore system acls" is set

vfs_acl_common: avoid setting POSIX ACLs if "ignore system acls" is set

When "ignore system acls" is set, do not mess at all with POSIX ACLS,
do not even calculate the would-be POSIX-ACL-based security descriptor
(for performance reasons).
Instead, just store a V3 blob with zero hash. This means that if we
later read the ACL without ignoring system ACLs, the NT ACL shall be
reset to the info derivable from the POSIX ACL.

File ownership is still modified as it has bearing on disk quotas.

BUG: https://bugzilla.samba.org/show_bug.cgi?id=11806

Signed-off-by: Uri Simchoni <uri@samba.org>
Reviewed-by: Jeremy Allison <jra@samba.org>
(cherry picked from commit 765e5f1f2670d3d5d8d62a04b4ccf38a680bcb37)