MEDIUM: tcp-sample: Rely on addresses at the appropriate level in tcp samples

MEDIUM: tcp-sample: Rely on addresses at the appropriate level in tcp samples

In src, src-port, dst and dst-port sample fetches, the client source and
destination addresses are retrieved from the appropriate level. It means
that, if the stream exits, we use the frontend stream-interface to get the
client source and destination addresses. Otherwise, the session is used. For
now, stream-interface or session addresses are never set. So, thanks to the
fallback mechanism, no changes are expected with this patch. But its purpose
is to rely on addresses at the appropriate level when set instead of those
at the connection level.