virtio-blk: Pass read errors to the guest

We need to signal not only write errors, but also read errors to the guest
driver. This fixes a regression introduced by 869a5c6d.

Signed-off-by: Kevin Wolf <kwolf@redhat.com>
Signed-off-by: Anthony Liguori <aliguori@us.ibm.com>
diff --git a/hw/virtio-blk.c b/hw/virtio-blk.c
index e6df9f2..42b766f 100644
--- a/hw/virtio-blk.c
+++ b/hw/virtio-blk.c
@@ -127,7 +127,7 @@
             return;
     }
 
-    virtio_blk_req_complete(req, VIRTIO_BLK_S_OK);
+    virtio_blk_req_complete(req, ret ? VIRTIO_BLK_S_IOERR : VIRTIO_BLK_S_OK);
 }
 
 static void virtio_blk_flush_complete(void *opaque, int ret)