test_nfs4_acls: Add test for mapping of special NFS4 ACL entries to DACL entries

test_nfs4_acls: Add test for mapping of special NFS4 ACL entries to DACL entries

In addition to entries for users and groups, NFSv4 ACLs have the concept
of entries for "special" entries. Only the "owner", "group" and
"everyone" entries are currently used in the ACL mapping.

Add a testcase that verifies the mapping from NFSv4 "special" entries to
the DACL in the security descriptor. Verify that only "owner", "group"
and "everyone" are mapped and all other "special" entries are ignored.

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>