Bug fix: Make D-Bus properties settable again.
* mandos (ClientDBus.notifychangeproperty/setter): Bug fix: pass
                                                   variant_level as a
                                                   keyword argument.
  (ClientDBus.Timeout_dbus_property): Bug fix: call function
                                      _timedelta_to_milliseconds in
                                      its new position as a global
                                      function.