Support name conflict check for dm-master/pd

[lichunzhu]

Bug Report

Please answer these questions before submitting your issue. Thanks!

1. What did you do?

a. Start a dm-cluster with 3 nodes, master1~3. b. Scale-out dm-cluster with 3 nodes, but the names are wrong. They are still master1~3 c. Fail to scale-out. Try to scale-in the newly added nodes. d. When tiup-dm scale-in, it will try to delete master1~3 and will affect the existing cluster.

2. What did you expect to see?

3. What did you see instead?

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

[lichunzhu]

1. If we support checking whether dm-master.name is conflicted before scale-out/deploy this won't happen.
2. If we want to delete member we need to make sure existing member doesn't have a seem name.