[PATCH v2] mlx5/testpmd: fix crash on quit with avail thresh enabled

[Matan Azrad]

From: Spike Du <spiked at nvidia.com>
> When testpmd quit with mlx5 avail_thresh enabled, a rte timer handler
> delays to reconfigure rx queue to re-arm this event. However at the same
> time, testpmd is destroying rx queues.
> It's never a valid use case for mlx5 avail_thresh. Before testpmd quit, user
> should disable avail_thresh configuration to not handle the events.
> This is documented in mlx5 driver guide.
> 
> To avoid the crash in such use case, check port status, if it is not
> RTE_PORT_STARTED, don't process the avail_thresh event.
> 
> Fixes: f41a5092e6ae ("app/testpmd: add host shaper command")
> Cc: stable at dpdk.org
> 
> Signed-off-by: Spike Du <spiked at nvidia.com>
Acked-by: Matan Azrad <matan at nvidia.com>