[SPARK-3007][SQL] Fixes dynamic partitioning support for lower Hadoop versions

This is a follow up of #2226 and #2616 to fix Jenkins master SBT build failures for lower Hadoop versions (1.0.x and 2.0.x).

The root cause is the semantics difference of `FileSystem.globStatus()` between different versions of Hadoop, as illustrated by the following test code:

```scala
object GlobExperiments extends App {
  val conf = new Configuration()
  val fs = FileSystem.getLocal(conf)
  fs.globStatus(new Path("/tmp/wh/*/*/*")).foreach { status =>
    println(status.getPath)
  }
}
```

Target directory structure:

```
/tmp/wh
├── dir0
│   ├── dir1
│   │   └── level2
│   └── level1
└── level0
```

Hadoop 2.4.1 result:

```
file:/tmp/wh/dir0/dir1/level2
```

Hadoop 1.0.4 resuet:

```
file:/tmp/wh/dir0/dir1/level2
file:/tmp/wh/dir0/level1
file:/tmp/wh/level0
```

In #2226 and #2616, we call `FileOutputCommitter.commitJob()` at the end of the job, and the `_SUCCESS` mark file is written. When working with lower Hadoop versions, due to the `globStatus()` semantics issue, `_SUCCESS` is included as a separate partition data file by `Hive.loadDynamicPartitions()`, and fails partition spec checking.  The fix introduced in this PR is kind of a hack: when inserting data with dynamic partitioning, we intentionally avoid writing the `_SUCCESS` marker to workaround this issue.

Hive doesn't suffer this issue because `FileSinkOperator` doesn't call `FileOutputCommitter.commitJob()`, instead, it calls `Utilities.mvFileToFinalPath()` to cleanup the output directory and then loads it into Hive warehouse by with `loadDynamicPartitions()`/`loadPartition()`/`loadTable()`. This approach is better because it handles failed job and speculative tasks properly. We should add this step to `InsertIntoHiveTable` in another PR.

Author: Cheng Lian <lian.cs.zju@gmail.com>

Closes #2663 from liancheng/dp-hadoop-1-fix and squashes the following commits:

0177dae [Cheng Lian] Fixes dynamic partitioning support for lower Hadoop versions
HOTFIX: Fix unicode error in merge script.

The merge script builds up a big command array and sometimes
this contains both unicode and ascii strings. This doesn't work
if you try to join them into a single string. Longer term a solution
is to go and make sure the source of all strings is unicode.

This patch provides a simpler solution... just print the array
rather than joining. I actually prefer printing an array here
anyways since joining on spaces is lossy in the case of arguments
that themselves contain spaces.

Author: Patrick Wendell <pwendell@gmail.com>

Closes #2645 from pwendell/merge-script and squashes the following commits:

167b792 [Patrick Wendell] HOTFIX: Fix unicode error in merge script.