Bug fixes: Make D-Bus properties settable again, and handle checkers for disabled clients correctly.
* 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. (Client.checked_ok): Bug fix: Handle disabled client. * mandos-ctl (main): Bug fix: Handle empty strings correctly.