Make sure log_dir is not the same with data_dir for TiKV cluster

[shenli]

Feature Request

Is your feature request related to a problem? Please describe:

If the log_dir is set as the same dir with data_dir, clean --log will remove the data in data_dir

Describe the feature you'd like:

Add a pre-flight check to make sure the two dirs are not the same one.

Describe alternatives you've considered:

None

Teachability, Documentation, Adoption, Migration Strategy:

None

[3pointer]

I think the directory is not the key problem. and we should not delete directory directly. if user choose to cleanup log. we need to make sure all files to be deleted have a suffix .log.

[AstroProfundis]

There are several improves we would do:

• Not allowing deployment of cluster if the log_dir is the same with data_dir or deploy_dir
• Not deleting anything if the log_dir is the same as data_dir on clean command
• Make experimental features with the “experimental” mark more visible
• Display list of files / directories to be deleted before the confirmation prompt
• Only delete files with .log extension on clean --log