[SPARK-4742][SQL] The name of Parquet File generated by AppendingParquetOutputFormat should be zero padded

When I use Parquet File as a output file using ParquetOutputFormat#getDefaultWorkFile, the file name is not zero padded while RDD#saveAsText does zero padding.

Author: Sasaki Toru <sasakitoa@nttdata.co.jp>

Closes #3602 from sasakitoa/parquet-zeroPadding and squashes the following commits:

6b0e58f [Sasaki Toru] Merge branch 'master' of git://github.com/apache/spark into parquet-zeroPadding
20dc79d [Sasaki Toru] Fixed the name of Parquet File generated by AppendingParquetOutputFormat