## What changes were proposed in this pull request?
When I ran self contained sql apps, such as
```scala
import org.apache.spark.sql.SparkSession
object ShowHiveTables {
def main(args: Array[String]): Unit = {
val spark = SparkSession
.builder()
.appName("Show Hive Tables")
.enableHiveSupport()
.getOrCreate()
spark.sql("show tables").show()
spark.stop()
}
}
```
with **yarn cluster** mode and `hive-site.xml` correctly within `$SPARK_HOME/conf`,they failed to connect the right hive metestore for not seeing hive-site.xml in AM/Driver's classpath.
Although submitting them with `--files/--jars local/path/to/hive-site.xml` or puting it to `$HADOOP_CONF_DIR/YARN_CONF_DIR` can make these apps works well in cluster mode as client mode, according to the official doc, see http://spark.apache.org/docs/latest/sql-programming-guide.html#hive-tables
> Configuration of Hive is done by placing your hive-site.xml, core-site.xml (for security configuration), and hdfs-site.xml (for HDFS configuration) file in conf/.
We may respect these configuration files too or modify the doc for hive-tables in cluster mode.
## How was this patch tested?
cc cloud-fan gatorsmile
Author: Kent Yao <yaooqinn@hotmail.com>
Closes#19663 from yaooqinn/SPARK-21888.
c755b0d910