tests/qtest: ahci-test: add test exposing reset issue with pending callback

tests/qtest: ahci-test: add test exposing reset issue with pending callback

Before commit "hw/ide: reset: cancel async DMA operation before
resetting state", this test would fail, because a reset with a
pending write operation would lead to an unsolicited write to the
first sector of the disk.

The test writes a pattern to the beginning of the disk and verifies
that it is still intact after a reset with a pending operation. It
also checks that the pending operation actually completes correctly.

Signed-off-by: Fiona Ebner <f.ebner@proxmox.com>
Message-ID: <20230906130922.142845-2-f.ebner@proxmox.com>
Signed-off-by: Philippe Mathieu-Daudé <philmd@linaro.org>