DRILL-2408 (part 2): CTAS should not create empty folders when underlying query returns no results
- changed ParquetRecordWriter to avoid creating the parquet file until the first row of data is available
- Moved unit tests in a separate test class that starts 3 drillbits, to test the case where multiple fragments are attempting to write empty parquet files
- changed BaseQueryTest to update the storage plugin in all started bits and not just the first one
