Fix bugs when VM shutdown with virtio-gpu unplugged

Fix bugs when VM shutdown with virtio-gpu unplugged

Virtio-gpu malloc memory for the queue when it realized, but the queues was not
released when it unrealized, which resulting in a memory leak. In addition,
vm_change_state_handler is not cleaned up, which is related to vdev and will
lead to segmentation fault when VM shutdown.

Signed-off-by: wangmeiling <wangmeiling21@huawei.com>
Signed-off-by: Binfeng Wu <wubinfeng@huawei.com>
Message-Id: <7bbbc0f3-2ad9-83ca-b39b-f976d0837daf@huawei.com>
Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>