topotato: need vtysh support for yang operational-data

[eqvinox]

e.g. show yang operational-data /frr-ripd:ripd ripd only works via vtysh, not directly on daemon

⇒ need to add a way to actually invoke vtysh instead of directly connecting to daemon

[eqvinox]

done (0f7e2917d43db7a59e2b6b0739e75cc13c0b45a7)