[SPARK-15569] Reduce frequency of updateBytesWritten function in Disk…

## What changes were proposed in this pull request?

Profiling a Spark job spilling large amount of intermediate data we found that significant portion of time is being spent in DiskObjectWriter.updateBytesWritten function. Looking at the code, we see that the function is being called too frequently to update the number of bytes written to disk. We should reduce the frequency to avoid this.

## How was this patch tested?

Tested by running the job on cluster and saw 20% CPU gain  by this change.

Author: Sital Kedia <skedia@fb.com>

Closes #13332 from sitalkedia/DiskObjectWriter.