BUG-8445: ignore responses from mismatched sessions

BUG-8445: ignore responses from mismatched sessions

We have to check the session ID of the response in order not to
wreck transmit consistency if face of leader changes and reconnects.

If we reconnect the connection to the new leader before we saw all
responses from the old leader, we end up in a situation where the
old leader completes some of the replayed messages before we either
send them to the new leader or receive (the correct) reply.

Guard against this by checking the session ID before attempting to
pair a response to a request.

Change-Id: I28fa98b89c679715c3a0c546962d00533e76aa5d
Signed-off-by: Robert Varga <robert.varga@pantheon.tech>