[SPARK-22793][SQL] Memory leak in Spark Thrift Server

# What changes were proposed in this pull request?
1. Start HiveThriftServer2.
2. Connect to thriftserver through beeline.
3. Close the beeline.
4. repeat step2 and step 3 for many times.
we found there are many directories never be dropped under the path `hive.exec.local.scratchdir` and `hive.exec.scratchdir`, as we know the scratchdir has been added to deleteOnExit when it be created. So it means that the cache size of FileSystem `deleteOnExit` will keep increasing until JVM terminated.

In addition, we use `jmap -histo:live [PID]`
to printout the size of objects in HiveThriftServer2 Process, we can find the object `org.apache.spark.sql.hive.client.HiveClientImpl` and `org.apache.hadoop.hive.ql.session.SessionState` keep increasing even though we closed all the beeline connections, which may caused the leak of Memory.

# How was this patch tested?
manual tests

This PR follw-up the apache#19989

Author: zuotingbing <[email protected]>

Closes apache#20029 from zuotingbing/SPARK-22793.

Author: zuotingbing

sql/hive/src/main/scala/org/apache/spark/sql/hive/HiveSessionStateBuilder.scala

@@ -42,7 +42,7 @@ class HiveSessionStateBuilder(session: SparkSession, parentState: Option[Session
    * Create a Hive aware resource loader.
    */
   override protected lazy val resourceLoader: HiveSessionResourceLoader = {
-    val client: HiveClient = externalCatalog.client.newSession()
+    val client: HiveClient = externalCatalog.client
     new HiveSessionResourceLoader(session, client)
   }