policychecker: allow i-dont-need-any-name configs

policychecker: allow i-dont-need-any-name configs

This allows configurations that do not concern any owned names, e.g.
configurations for specifying who can receive some specific signals.

Without this change, the checking rules ensure that every policy
configuration file contains at least one <deny send_destination/prefix>
and one <deny own> policy rule. This was introduced when there
was "global default allow" policy in some uses. Nowadays, such policies
are probably long gone.

Anyway, there are still other checking rules present, which complain for
not having proper <deny> rules in default context, if <allow>
rules for a name are present in the configuration file.

Change-Id: Ic4eeee3ff5c8524fda58d17874fe6fdb37fb4d1c