[SPARK-3967] don’t redundantly overwrite executor JAR deps

Fairly minor style nit, but do you mind indenting these method parameters by two more spaces, like `fetchFile` above:

```
   def fetchFile(
       url: String,
       targetDir: File,
       conf: SparkConf,
       securityMgr: SecurityManager,
       hadoopConf: Configuration,
       timestamp: Long,
       useCache: Boolean) {
     val fileName = url.split("/").last
```

This is a really minor style point that I've been guilty of overlooking myself: https://cwiki.apache.org/confluence/display/SPARK/Spark+Code+Style+Guide