test_nfs4_acls: Add test for acedup settings

test_nfs4_acls: Add test for acedup settings

The NFSv4 ACL mapping code has a setting nfs4:acedup. Depending on the
setting, when mapping from DACLs to NFSv4 ACLs, duplicate ACL entries
are either merged, ignored or rejected. Add a testcase that has
duplicate ACL entries and verify the expected behavior for all possible
settings of the nfs4:acedup option.

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>