[release-branch.go1.11] net/http: update bundled x/net/http2

This updates x/net/http2 to x/net on the latest commit of x/net on
release-branch.go1.11 branch, golang/net@a4630153038d3cb8c57f, for:

	[release-branch.go1.11] http2: don't leak streams on broken body
	https://golang.org/cl/154237

Fixes #28673

Change-Id: I8f40c69502fa95d1d9dff1ab68444640444442aa
Reviewed-on: https://go-review.googlesource.com/c/154298
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>
Run-TryBot: Brad Fitzpatrick <bradfitz@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
diff --git a/src/net/http/h2_bundle.go b/src/net/http/h2_bundle.go
index 12cf65f..2cd2b86 100644
--- a/src/net/http/h2_bundle.go
+++ b/src/net/http/h2_bundle.go
@@ -7705,6 +7705,7 @@
 			default:
 			}
 			if err != nil {
+				cc.forgetStreamID(cs.ID)
 				return nil, cs.getStartedWrite(), err
 			}
 			bodyWritten = true
@@ -7826,6 +7827,7 @@
 			sawEOF = true
 			err = nil
 		} else if err != nil {
+			cc.writeStreamReset(cs.ID, http2ErrCodeCancel, err)
 			return err
 		}