[SPARK-23275][SQL] hive/tests have been failing when run locally on the laptop (Mac) with OOM

## What changes were proposed in this pull request?
hive tests have been failing when they are run locally (Mac Os) after a recent change in the trunk. After running the tests for some time, the test fails with OOM with Error: unable to create new native thread.

I noticed the thread count goes all the way up to 2000+ after which we start getting these OOM errors. Most of the threads seem to be related to the connection pool in hive metastore (BoneCP-xxxxx-xxxx ). This behaviour change is happening after we made the following change to HiveClientImpl.reset()

``` SQL
 def reset(): Unit = withHiveState {
    try {
      // code
    } finally {
      runSqlHive("USE default")  ===> this is causing the issue
    }
```
I am proposing to temporarily back-out part of a fix made to address SPARK-23000 to resolve this issue while we work-out the exact reason for this sudden increase in thread counts.

## How was this patch tested?
Ran hive/test multiple times in different machines.

(If this patch involves UI changes, please attach a screenshot; otherwise, remove this)

Please review http://spark.apache.org/contributing.html before opening a pull request.

Author: Dilip Biswal <[email protected]>

Closes #20441 from dilipbiswal/hive_tests.

Author: dilipbiswal

sql/hive/src/main/scala/org/apache/spark/sql/hive/client/HiveClientImpl.scala

@@ -825,23 +825,19 @@ private[hive] class HiveClientImpl(
   }
 
   def reset(): Unit = withHiveState {
-    try {
-      client.getAllTables("default").asScala.foreach { t =>
-        logDebug(s"Deleting table $t")
-        val table = client.getTable("default", t)
-        client.getIndexes("default", t, 255).asScala.foreach { index =>
-          shim.dropIndex(client, "default", t, index.getIndexName)
-        }
-        if (!table.isIndexTable) {
-          client.dropTable("default", t)
-        }
+    client.getAllTables("default").asScala.foreach { t =>
+      logDebug(s"Deleting table $t")
+      val table = client.getTable("default", t)
+      client.getIndexes("default", t, 255).asScala.foreach { index =>
+        shim.dropIndex(client, "default", t, index.getIndexName)
       }
-      client.getAllDatabases.asScala.filterNot(_ == "default").foreach { db =>
-        logDebug(s"Dropping Database: $db")
-        client.dropDatabase(db, true, false, true)
+      if (!table.isIndexTable) {
+        client.dropTable("default", t)
       }
-    } finally {
-      runSqlHive("USE default")
+    }
+    client.getAllDatabases.asScala.filterNot(_ == "default").foreach { db =>
+      logDebug(s"Dropping Database: $db")
+      client.dropDatabase(db, true, false, true)
     }
   }
 }