test_nfs4_acls: Add test for mapping from DACL to NFS4 ACL with config special

test_nfs4_acls: Add test for mapping from DACL to NFS4 ACL with config 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 DACL in the
security descriptor to the NFSv4 ACL.

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>