Correctly check socket on stream creation

[JamesNK]

Fixes #2210

I recreated the error from #2210. The previous fix (socket timeout) will address this issue for the vast majority of people. However, some servers may have configured a timeout of less than 60 seconds. They could still run into problems.

Previously if a server had written data to the socket (e.g. HTTP/2 GOAWAY frame) and closed it, then it would incorrectly be seen as healthy. This PR updates the stream creation method to correctly check that a socket is still healthy before using it. This involves reusing the check logic from the ping that reads available data. When available data is read, the client will see the socket is closed and create a new one for the connection.

[amcasey]

Seems sensible to me. I don't consider any of my suggestions blocking.