[SPARK-14959][SQL] handle partitioned table directories in distributed filesystem

## What changes were proposed in this pull request?
##### The root cause:
When `DataSource.resolveRelation` is trying to build `ListingFileCatalog` object, `ListLeafFiles` is invoked where a list of `FileStatus` objects are retrieved from the provided path. These FileStatus objects include directories for the partitions (id=0 and id=2 in the jira). However, these directory `FileStatus` objects also try to invoke `getFileBlockLocations` where directory is not allowed for `DistributedFileSystem`, hence the exception happens.

This PR is to remove the block of code that invokes `getFileBlockLocations` for every FileStatus object of the provided path. Instead, we call `HadoopFsRelation.listLeafFiles` directly because this utility method filters out the directories before calling `getFileBlockLocations` for generating `LocatedFileStatus` objects.

## How was this patch tested?
Regtest is run. Manual test:
```
scala> spark.read.format("parquet").load("hdfs://bdavm009.svl.ibm.com:8020/user/spark/SPARK-14959_part").show
+-----+---+
| text| id|
+-----+---+
|hello|  0|
|world|  0|
|hello|  1|
|there|  1|
+-----+---+

       spark.read.format("orc").load("hdfs://bdavm009.svl.ibm.com:8020/user/spark/SPARK-14959_orc").show
+-----+---+
| text| id|
+-----+---+
|hello|  0|
|world|  0|
|hello|  1|
|there|  1|
+-----+---+
```
I also tried it with 2 level of partitioning.
I have not found a way to add test case in the unit test bucket that can test a real hdfs file location. Any suggestions will be appreciated.

Author: Xin Wu <xinwu@us.ibm.com>

Closes #13463 from xwu0226/SPARK-14959.