PR #3499 introduces two new transport parameters:

• handshake_connection_id, set by each peer as source CID of Initial packets
• retry_connection_id, set by a server that sent a Retry to the source CID of the Retry packet.

We expect that the PR will be included in draft-28, but it is useful to do some tests by adding the code now to at least some implementations of draft-27. Note that sending new transport parameters should not cause interop issues since implementations are supposed to ignore unknown TPs. The expectations for the early testing are:

1. Always send the handshake_connection_id TP.
2. Send the retry_connection_id TP when required by PR #3499.
3. Verify that the client is not sending retry_connection_id TP.
4. If the peer sent a handshake_connection_id TP, perform all the checks specified in PR #3499.
5. If receiving an Initial packet after sending a Retry, verify that the DCID matches the Retry CID.
6. If receiving original_connection_id from the server, verify that it matches even if no retry was received.

The goal is to get some early deployment and verify the PR.