Do the bootstrap only in the owner node.

[winkyao]

We will do some DDL and DML works when the cluster is not bootstrapped.

https://github.com/pingcap/tidb/blob/master/session/bootstrap.go#L252

But if we start multi tidb notes on a new cluster, it will do the same bootstrap works in all the notes. Which will cause write conflict and some errors.

Actually, the DDL is only handled by the owner note, so we can figure out whether the node is the owner, and then do the bootstrap, otherwise wait for the cluster to upgrade/bootstrap to the expected version.