Add execution of SHOW TABLES before TestHive.reset().

Author: ueshin

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

@@ -26,6 +26,9 @@ import scala.collection.JavaConversions._
  * A set of test cases that validate partition and column pruning.
  */
 class PruningSuite extends HiveComparisonTest {
+  // MINOR HACK: You must run a query before calling reset the first time.
+  TestHive.hql("SHOW TABLES")
+
   // Column/partition pruning is not implemented for `InMemoryColumnarTableScan` yet, need to reset
   // the environment to ensure all referenced tables in this suites are not cached in-memory.
   // Refer to https://issues.apache.org/jira/browse/SPARK-2283 for details.