block/nbd: Delete reconnect delay timer when done

We start the reconnect delay timer to cancel the reconnection attempt
after a while.  Once nbd_co_do_establish_connection() has returned, this
attempt is over, and we no longer need the timer.

Delete it before returning from nbd_reconnect_attempt(), so that it does
not persist beyond the I/O request that was paused for reconnecting; we
do not want it to fire in a drained section, because all sort of things
can happen in such a section (e.g. the AioContext might be changed, and
we do not want the timer to fire in the wrong context; or the BDS might
even be deleted, and so the timer CB would access already-freed data).

Reviewed-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
Signed-off-by: Hanna Reitz <hreitz@redhat.com>
Signed-off-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>

block/nbd.c

@@ -381,6 +381,13 @@ static coroutine_fn void nbd_reconnect_attempt(BDRVNBDState *s)
     }
 
     nbd_co_do_establish_connection(s->bs, NULL);
+
+    /*
+     * The reconnect attempt is done (maybe successfully, maybe not), so
+     * we no longer need this timer.  Delete it so it will not outlive
+     * this I/O request (so draining removes all timers).
+     */
+    reconnect_delay_timer_del(s);
 }
 
 static coroutine_fn int nbd_receive_replies(BDRVNBDState *s, uint64_t handle)