(PR#10078) AIs often agress on cease fire just for one turn

<URL: http://rt.freeciv.org/Ticket/Display.html?id=10078 >

i suggest temporary fix for it:
    if (aplayer->is_alive
        && adip->at_war_with_ally
        && !adip->is_allied_with_ally
        && !pplayers_at_war(pplayer, aplayer) &&
        && (diplomatic_state != DS_CEASEFIRE || myrand(5) < 1)) {
             ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
      notify(aplayer, _("*%s (AI)* Your aggression against my allies was "
			"your last mistake!"), pplayer->name);
      ai_go_to_war(pplayer, ai, aplayer);
    }

The player will have some time to sign a ceasefire with the rest of the
alliance, before someone declares war again
--
mateusz