Cancel autoping timer on disconnect or connection loss

If Profanity is disconnected in any way before ping response is
received, the autoping timer will expire after the next connection
is established. As result, user will be disconnected immediately.

Cancel autoping timer in ev_disconnect_cleanup(), so it is done
for all kind of disconnections.

src/event/common.c

@@ -53,6 +53,7 @@ ev_disconnect_cleanup(void)
     ui_disconnected();
     session_disconnect();
     roster_destroy();
+    iq_autoping_timer_cancel();
     muc_invites_clear();
     muc_confserver_clear();
     chat_sessions_clear();