[release-branch.go1.11] http2: don't leak streams on broken body

[386898917]

Updates golang/go#28673

Change-Id: I5d9a643f33d27d33b24f670c98f5a51aa6000967
GitHub-Last-Rev: 3ac4a57
GitHub-Pull-Request: #18
Reviewed-on: https://go-review.googlesource.com/c/132715
Run-TryBot: Brad Fitzpatrick bradfitz@golang.org
TryBot-Result: Gobot Gobot gobot@golang.org
Reviewed-by: Brad Fitzpatrick bradfitz@golang.org
(cherry picked from commit 1c5f79c)
Reviewed-on: https://go-review.googlesource.com/c/154237

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