[dnsdist] DoH: 302 redirecting / to a help page

[Stephane Bortzmeyer]

On Mon, Sep 16, 2019 at 04:24:33PM +0200,
 Daniel Stirnimann <daniel.stirnimann at switch.ch> wrote 
 a message of 30 lines which said:

> If your request went over IPv6 then this is expected because you added
> the supportpagemap only on your IPv4 listener. Make sure you also add:

It works, thanks.

> Note also, the newDOHResponseMapEntry first argument is a regex. You may
> want to make it more specific, e.g. "^/about$

Yes but, because it failed, I made it more lax, to see if it was a
regex problem. Now, everything is fine.