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

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

Add testcase for mapping from entries in the DACL security descriptor to
"special" entries in the NFSv4 ACL. Verify that the WORLD well-known SID
maps to "everyone" in the NFSv4 ACL. Verify that the "Unix NFS" SID is
ignored, as there is no meaningful mapping for this entry. Verify that
SID entries matching the owner or group are mapped to "special owner"
or "special group", but only if no inheritance flags are used. "special
owner" and "special group" with inheritance flags have the meaning of
CREATOR OWNER and CREATOR GROUP and will be tested in another testcase.

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>