check if dir exist before deploy/scale-out

[nexustar]

Bug Report

Please answer these questions before submitting your issue. Thanks!

1. What did you do?

1. deploy tidb with grafana

2. deploy dm without dm

3. scale-out a grafana to dm cluster with same dir

4. What did you expect to see?

scale-out failed

6. What did you see instead?

scale-out succeed

7. What version of TiUP are you using (tiup --version)?