OSPF: Reference_bandwidth is copied into vrfs, but some of the templates don't reference it there

[jbemmel]

https://github.com/ipspace/netlab/blob/82df11814bf2c71dade70453c6f85da6c27d0bb9/netsim/modules/ospf.py#L58

I was working on the Dell OS10 VRF template, adding a fix for reference_bandwidth in case of VRFs - but noticed that many of the other templates have the same issue.

I don't see a good use case for having reference_bandwidth set to a different value at the VRF level, so we could also decide to only have it globally. But since it's copied, it should be referenced