tikv needs create directories manually before start log backup for local storage

## Bug Report

Please answer these questions before submitting your issue. Thanks!

### 1. Minimal reproduce step (Required)

1. create parent directories of log backup path in tikv nodes.
2. start log backup

### 2. What did you expect to see? (Required)

when execute log status command, there is no checkpoint ts of store nodes.

when `ls` log backup path in tikv nodes, there is no backup files.

### 3. What did you see instead (Required)

log backup files can flush to local storage. log status command can show correct task status.

### 4. What is your TiDB version? (Required)