should remove targetFile when targetFile is existing?

Nobody has claimed this yet.

when the current file should roll，the operation is
`fs.move(sourceFilePath, targetFilePath, { overwrite: true });`
this will delete target file if it exist.
But, in the mutli process app，when set disableClustering: true, all process will do the same operation. The first write log process will rename log.log to log.log.2020-01-01-01 and renew log.log. The next write log process will rename log.log that is renewed by first process to log.log.2020-01-01-01 too and this cause log loss.

So, when target file exists, should skip remove operation?
`try {
if (fs.existsSync(targetFilePath)) {
return ;
}
await fs.move(sourceFilePath, targetFilePath, { overwrite: true });
} catch (e) { }`

Start by tracing the rollover path that calls fs.move(sourceFilePath, targetFilePath, { overwrite: true }) and reproduce the disableClustering: true multi-process case. Confirm the behavior when targetFilePath already exists; done means concurrent rollovers no longer overwrite the renewed log or cause log loss.

Written by the indexing model from the issue text.