qemu-iotests: Use host_device instead of file in 149

The test case uses block devices with driver=file, which causes the test
to fail after commit 230ff73904 added a deprecation warning for this.
Fix the test case to use driver=host_device and update the reference
output accordingly.

Signed-off-by: Kevin Wolf <kwolf@redhat.com>

tests/qemu-iotests/149

@@ -259,7 +259,7 @@ def qemu_io_image_args(config, dev=False):
     if dev:
         return [
             "--image-opts",
-            "driver=file,filename=%s" % config.device_path()]
+            "driver=host_device,filename=%s" % config.device_path()]
     else:
         return [
             "--object",