CVE-2020-25722 selftest/user_account_control: more work to cope with UAC/objectclass...

CVE-2020-25722 selftest/user_account_control: more work to cope with UAC/objectclass defaults and lock

This new restriction breaks a large number of assumptions in the tests, like
that you can remove some UF_ flags, because it turns out doing so will
make the 'computer' a 'user' again, and this will fail.

BUG: https://bugzilla.samba.org/show_bug.cgi?id=14753

Signed-off-by: Andrew Bartlett <abartlet@samba.org>
Reviewed-by: Douglas Bagnall <douglas.bagnall@catalyst.net.nz>