Overriding dest_addr does not override Host header, leading to connection failures on some cloud WAFs

[dkegel-fastly]

This makes it hard to test WAFs running on hosting providers that rely on the Host header.

Overriding Host in applyInputOverride where it overrides DestAddr seems to fix this, draft PR coming.

[theseion]

Thanks @dkegel-fastly. I'm working on it.