x/net/http2: RoundTrip does not close request body after early errors

[neild]

The RoundTrip contract states that the request body should be closed by RoundTrip, even when an error occurs.

The HTTP/2 RoundTrip does not close the request body in various situations:

• If the request is invalid: transport.go#1011 and in subsequent failures early in request processing.
• If an open slot cannot be acquired on the selected ClientConn: transport.go#1026
• If a new request body is acquired from GetBody: transport.go#550 (While the exact handling of bodies created by GetBody is not fully documented, the HTTP/1 RoundTrip implementation closes both the original Request.Body and every body returned by Request.GetBody.)

[gopherbot]

Change https://golang.org/cl/349489 mentions this issue: http2: close request body after early RoundTrip failures