MINOR: http-ana: Use -1 status for client aborts during queuing and connect

MINOR: http-ana: Use -1 status for client aborts during queuing and connect

When a client aborts while the session is in the queue or during the connect
stage, instead of reporting a 503-Service-Unavailable error in logs, -1
status is used. It means -1 status is now reported with 'CC' and 'CQ'
termination state.

Indeed, when a client aborts before the server connection is established,
there is no reason to report a 503 because nothing is sent to the
server. And in this case, because it is a client abort, it is useless to
send any response to the client. Thus -1 status is approriate. This status
is used in log messages when the connection is closed and no response is
sent.

This patch should fix the issue #1266.