selftest: Start implementing unit test for nfs4_acls

selftest: Start implementing unit test for nfs4_acls

Existing smbtorture tests set and query ACLs through SMB, only working
with the DACLs in the Security Descriptors, but never check the NFSv4
ACL representation. This patch introduces a unit test to verify the
mapping between between Security Descriptors and NFSv4 ACLs. As the
mapping code queries id mappings, the id mapping cache is first primed
with the mappings used by the tests and those mappings are removed again
during teardown.

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>