net/http/httputil: don't add X-Forwarded-{Host,Proto} after invoking Director funcs
This reverts CL 407414.
When forwarding an inbound request that contains an existing
X-Forwarded-Host or X-Forwarded-Proto header, a proxy might want
to preserve the header from the inbound request, replace it with
its own header, or not include any header at all.
CL 407414 replaces inbound X-Forwarded-{Host,Proto} headers by default,
and allows a Director func to disable sending these headers at all.
However, the Director hook API isn't sufficiently flexible to permit the
previous behavior of preserving inbound values unchanged.
The new Rewrite API does have this flexibility; users of Rewrite can
easily pick the exact behavior they want.
Revert the change to ReverseProxy when using a Director func.
Users who want a convenient way to set X-Forwarded-* headers to
reasonable values can migrate to Rewrite at their convenience,
and users depending on the current behavior will be unaffected.
For #50465.
Fixes #57132.
Change-Id: Ic42449c1bb525d6c9920bf721efbc519697f4f20
Reviewed-on: https://go-review.googlesource.com/c/go/+/457595
Run-TryBot: Damien Neil <dneil@google.com>
TryBot-Result: Gopher Robot <gobot@golang.org> Reviewed-by: Roland Shoemaker <roland@golang.org>