Allow pfdns to return local address of portal instead of VIP

[julsemaan]

Is your feature request related to a problem? Please describe. In some cases we may want to send users to the local server IP of the portal instead of the VIP in order to better distribute the load.

Describe the solution you'd like A setting in the cluster section to enable this behavior (disabled by default)

Describe alternatives you've considered Using the VIP but it has its limitations

[julsemaan]

We should discuss if this is a good idea or not before implementing this

[extrafu]

Unsure about this one unless the TTL is low and even for that, some OS do their own agressive caching and if we don't return the VIP and the node goes down, the portal won't be reachable for some devices with bogus cached entries. Also, I do think it makes things harder to debug.