test: early server response with data

[DDtKey]

• fix of the test's name after changing it in #634
• additional test that server also sends data frames correctly

This is normal scenario and I decided to extend test a bit.

[DDtKey]

And also this is preliminary change to handle NO_ERROR correctly on client side in (h2 or hyper` - ?), because currently such case causes:

hyper::Error(Body, Error { kind: Reset(StreamId(3), NO_ERROR, Remote) }

While request was handled correctly (for example, reaching max request body size) and the response was sent.