[BUG] Qualification tool really slow writing to DBFS

[tgravescs]

Describe the bug
I was running qualification tool and writing to DBFS and it takes a really long time to write the csv files. It took like 10 hours to run qualification tool on 7 different batches of 1000 event logs, where the parsing of event log itself was very fast but writing of the summary csv, exec and stages csv took a very long time. I'm not sure if this is any different than S3, we may want to measure. Perhaps it would be faster to write to local disk and then copy into DBFS or S3.

investigate more and make changes or document best practices