BUG/MINOR: session: mark the handshake as complete earlier

There is a small waste of CPU cycles when no handshake is required on an
accepted connection, because we had to perform one call to conn_fd_handler()
to mark the connection CONNECTED and to call process_session() again to say
that nothing happened.

By marking the connection CONNECTED when there is no pending handshake, we
avoid this extra call to process_session().

src/session.c

@@ -210,7 +210,8 @@ int session_accept(struct listener *l, int cfd, struct sockaddr_storage *addr)
 		return 1;
 	}
 
-	/* OK let's complete session initialization */
+	/* OK let's complete session initialization since there is no handshake */
+	s->si[0].conn->flags |= CO_FL_CONNECTED;
 	ret = session_complete(s);
 	if (ret > 0)
 		return ret;