*: Modify agentx to be allowed to be called

[donaldsharp]

If you had a situation where an operator turned on ospfd with snmp but not ospf6d and agentx was configured then you get into a situation where ospf6d would complain that the config for agentx did not exist. Let's modify the code to allow this situation to happen.

Fixes: #15896

[ton31337]

@Mergifyio backport stable/10.0

[mergify[bot]]

backport stable/10.0

✅ Backports have been created

• #16051 *: Modify agentx to be allowed to be called (backport #15980) has been created for branch stable/10.0 but encountered conflicts

[eqvinox]

I think this can be done better in vtysh; I'll try doing that & open a PR — if there's nothing in a few days I have clearly failed and this can proceed :laughing:

[ton31337]

A few days passed, does it mean clearly failed? :smile: