Ensure gateway-enabled int will be UP by the latest

That should change the 'point of appliance' for
https://github.com/Mirantis/fuel/blob/master/deployment/puppet/l23network/manifests/l3/ifconfig.pp#L299-L302
to ensure default route will be created at the very end of interfaces' configuration and startup.

Signed-off-by: Bogdan Dobrelya <bogdando@mail.ru>