tests/virtio-blk-test: Disable auto-read-only

tests/virtio-blk-test uses a temporary image file that it deletes while
QEMU is still running, so it can't be reopened when writers are
attached or detached. Disable auto-read-only to keep it always writable.
Signed-off-by: NKevin Wolf <kwolf@redhat.com>
Reviewed-by: NEric Blake <eblake@redhat.com>

tests/virtio-blk-test.c

@@ -751,7 +751,7 @@ static void *virtio_blk_test_setup(GString *cmd_line, void *arg)
     char *tmp_path = drive_create();
 
     g_string_append_printf(cmd_line,
-                           " -drive if=none,id=drive0,file=%s,format=raw "
+                           " -drive if=none,id=drive0,file=%s,format=raw,auto-read-only=off "
                            "-drive if=none,id=drive1,file=null-co://,format=raw ",
                            tmp_path);