net/http: update bundled http2; fixes TestTransportAndServerSharedBodyRace_h2
Update bundled http2 to git rev
d1ba260648 (https://golang.org/cl/18288).
Fixes the flaky TestTransportAndServerSharedBodyRace_h2.
Also adds some debugging to TestTransportAndServerSharedBodyRace_h2
which I hope won't ever be necessary again, but I know will be.
Fixes #13556
Change-Id: Ibcf2fc23ec0122dcac8891fdc3bd7f8acddd880e
Reviewed-on: https://go-review.googlesource.com/18289
Reviewed-by: Andrew Gerrand <adg@golang.org>
Run-TryBot: Brad Fitzpatrick <bradfitz@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>