OSPF default interface passive

[jbemmel]

Cisco provides a way to configure OSPF interfaces as passive by default, which is useful for configurations with many VLAN interfaces

I propose that Netlab support the same, by allowing users to configure ospf.passive: True as a global default

[ipspace]

We could add 'passive' as global/node attribute that is copied into interfaces (same as OSPF area), but what's wrong with VLAN groups?

[jbemmel]

Nothing, but [preaching to the choir] OSPF is independent of VLANs and there could be a mix of interfaces, all of which I'd want to be passive by default

[ipspace]

OK. Submit a PR.