Allow different protocol version when trying to reuse a session

We now send the highest supported version by the client, even if the session
uses an older version.

This fixes 2 problems:
- When you try to reuse a session but the other side doesn't reuse it and
  uses a different protocol version the connection will fail.
- When you're trying to reuse a session with an old version you might be
  stuck trying to reuse the old version while both sides support a newer
  version

Signed-off-by: Kurt Roeckx <kurt@roeckx.be>
Reviewed-by: Viktor Dukhovni <viktor@openssl.org>

GH: #852, MR: #2452