[SPARK-10216][SQL] Avoid creating empty files during overwriting with group by query

## What changes were proposed in this pull request?

Currently, `INSERT INTO` with `GROUP BY` query tries to make at least 200 files (default value of `spark.sql.shuffle.partition`), which results in lots of empty files.

This PR makes it avoid creating empty files during overwriting into Hive table and in internal data sources  with group by query.

This checks whether the given partition has data in it or not and creates/writes file only when it actually has data.

## How was this patch tested?

Unittests in `InsertIntoHiveTableSuite` and `HadoopFsRelationTest`.

Closes #8411

Author: hyukjinkwon <gurwls223@gmail.com>
Author: Keuntae Park <sirpkt@apache.org>

Closes #12855 from HyukjinKwon/pr/8411.