Fix failure with unnumbered BGP neighours and don't report VLAN interfaces as down

[SapphirusBeryl]

- What I did

• Skip unnumbered BGP neighours instead of failing
• Don't report VLAN interfaces as oper_down

- How I did it

1. In case of unnumbered BGP, the neighbor is an interface.
   That can't be represented here, so just skip the neighbor.
2. VLAN interfaces don't have an operational status, so
   return admin status for them

- How to verify it

1. Unnumbered BGP neighours no longer trigger a failure
2. VLAN Interfaces are no longer reported as down

- Description for the changelog

• Skip unnumbered BGP neighours instead of failing
• Don't report VLAN interfaces as oper_down

[linux-foundation-easycla]

• ✅login: lukasstockner / (7a88058)
• ✅login: lukasstockner / (7a88058, a1e11f8)
• ✅login: SapphirusBeryl / (d443ed2)

The committers listed above are authorized under a signed CLA.