incusd/instance/qemu: Fix shutdown race

Signed-off-by: Stéphane Graber <stgraber@stgraber.org>

internal/server/instance/drivers/driver_qemu.go

@@ -757,17 +757,8 @@ func (d *qemu) Shutdown(timeout time.Duration) error {
 	// Wait 500ms for the first event to be received by the guest.
 	time.Sleep(500 * time.Millisecond)
 
-	// Send a second system_powerdown command (required to get Windows to shutdown).
-	err = monitor.Powerdown()
-	if err != nil {
-		if err == qmp.ErrMonitorDisconnect {
-			op.Done(nil)
-			return nil
-		}
-
-		op.Done(err)
-		return err
-	}
+	// Attempt to send a second system_powerdown command (required to get Windows to shutdown).
+	_ = monitor.Powerdown()
 
 	d.logger.Debug("Shutdown request sent to instance")