x/net/http2: stuck extended CONNECT requests #70658
Description
@aojea points out in https://go-review.googlesource.com/c/net/+/610977/comment/2f78d788_69fe1833/ that HTTP/2 extended CONNECT requests can get stuck waiting for a SETTINGS frame, due to a failure to close ClientConn.seenSettingsChan on some error paths.