fix(http2): improve I/O errors emitted by H2Upgraded (#2598)
fix(http2): improve I/O errors emitted by H2Upgraded (#2598)

When a `CONNECT` over HTTP2 has been established, and the user tries to write data right when the peer closes the stream, it will no longer return as a "user error". The reset code is checked, and converted into an appropriate `io::ErrorKind`.
tshepang/hyper,tshepang/hyper,tshepang/hyper,hyperium/hyper,hyperium/hyper,hyperium/hyper