http.TimeFormat hard-codes GMT and is documented that:

> TimeFormat is the time format to use when generating times in HTTP
> headers. It is like time.RFC1123 but hard-codes GMT as the time
> zone. The time being formatted must be in UTC for Format to generate
> the correct format.

These two users weren't UTC-ifying the time.Time first.

Fixes golang/go#25015

Change-Id: I82be01856260e363361137fd9651b1940f439f21
Reviewed-on: https://go-review.googlesource.com/113795
Run-TryBot: Brad Fitzpatrick <bradfitz@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Filippo Valsorda <filippo@golang.org>