[SPARK-12971] Fix Hive tests which fail in Hadoop-2.3 SBT build

ErrorPositionSuite and one of the HiveComparisonTest tests have been consistently failing on the Hadoop 2.3 SBT build (but on no other builds). I believe that this is due to test isolation issues (e.g. tests sharing state via the sets of temporary tables that are registered to TestHive).

This patch attempts to improve the isolation of these tests in order to address this issue.

Author: Josh Rosen <joshrosen@databricks.com>

Closes #10884 from JoshRosen/fix-failing-hadoop-2.3-hive-tests.

sql/hive/src/test/scala/org/apache/spark/sql/hive/ErrorPositionSuite.scala

@@ -19,20 +19,34 @@ package org.apache.spark.sql.hive
 
 import scala.util.Try
 
-import org.scalatest.BeforeAndAfter
+import org.scalatest.BeforeAndAfterEach
 
 import org.apache.spark.sql.{AnalysisException, QueryTest}
 import org.apache.spark.sql.catalyst.parser.ParseDriver
 import org.apache.spark.sql.catalyst.util.quietly
 import org.apache.spark.sql.hive.test.TestHiveSingleton
 
-class ErrorPositionSuite extends QueryTest with TestHiveSingleton with BeforeAndAfter {
+class ErrorPositionSuite extends QueryTest with TestHiveSingleton with BeforeAndAfterEach {
   import hiveContext.implicits._
 
-  before {
+  override protected def beforeEach(): Unit = {
+    super.beforeEach()
+    if (sqlContext.tableNames().contains("src")) {
+      sqlContext.dropTempTable("src")
+    }
+    Seq((1, "")).toDF("key", "value").registerTempTable("src")
     Seq((1, 1, 1)).toDF("a", "a", "b").registerTempTable("dupAttributes")
   }
 
+  override protected def afterEach(): Unit = {
+    try {
+      sqlContext.dropTempTable("src")
+      sqlContext.dropTempTable("dupAttributes")
+    } finally {
+      super.afterEach()
+    }
+  }
+
   positionTest("ambiguous attribute reference 1",
     "SELECT a from dupAttributes", "a")
 

sql/hive/src/test/scala/org/apache/spark/sql/hive/execution/HiveComparisonTest.scala

@@ -150,7 +150,11 @@ abstract class HiveComparisonTest
        """.stripMargin
     })
 
-    super.afterAll()
+    try {
+      TestHive.reset()
+    } finally {
+      super.afterAll()
+    }
   }
 
   protected def prepareAnswer(