test_nfs4_acls: Add test for mapping from NFS4 to DACL in config mode special

test_nfs4_acls: Add test for mapping from NFS4 to DACL in config mode special

The mapping code between NFSv4 ACLs and security descriptors still has
the deprecated config setting "nfs4:mode = special". This should not be
used as it has security problems: All entries matching owner or group
are mapped to "special owner" or "special group", which can change its
meaning when being inherited to a new file or directory with different
owner and owning group.

This mode should eventually be removed, but as long as it still exists
add testcases to verify the expected behavior. This patch adds the
testcase for "nfs4:mode = special" when mapping from the NFS4 ACL to the
DACL in the security descriptor.

BUG: https://bugzilla.samba.org/show_bug.cgi?id=14032

Signed-off-by: Christof Schmitt <cs@samba.org>
Reviewed-by: Ralph Boehme <slow@samba.org>