http2: do not retry dial if request context canceled

When request context is canceled or expired, do not retry on dialing to the server.

http2/client_conn_pool.go

@@ -300,6 +300,10 @@ func shouldRetryDial(call *dialCall, req *http.Request) bool {
 		// from this request.
 		return false
 	}
+	if req.Context().Err() != nil {
+		// If the request is canceled or expired, should not retry.
+		return false
+	}
 	if !errors.Is(call.err, context.Canceled) && !errors.Is(call.err, context.DeadlineExceeded) {
 		// If the call error is not because of a context cancellation or a deadline expiry,
 		// the dial should not be retried.