[SPARK-12742][SQL] org.apache.spark.sql.hive.LogicalPlanToSQLSuite failure due...

[SPARK-12742][SQL] org.apache.spark.sql.hive.LogicalPlanToSQLSuite failure due to Table already exists exception

```
[info] Exception encountered when attempting to run a suite with class name:
org.apache.spark.sql.hive.LogicalPlanToSQLSuite *** ABORTED *** (325 milliseconds)
[info]   org.apache.spark.sql.AnalysisException: Table `t1` already exists.;
[info]   at org.apache.spark.sql.DataFrameWriter.saveAsTable(DataFrameWriter.scala:296)
[info]   at org.apache.spark.sql.DataFrameWriter.saveAsTable(DataFrameWriter.scala:285)
[info]   at org.apache.spark.sql.hive.LogicalPlanToSQLSuite.beforeAll(LogicalPlanToSQLSuite.scala:33)
[info]   at org.scalatest.BeforeAndAfterAll$class.beforeAll(BeforeAndAfterAll.scala:187)
[info]   at org.apache.spark.sql.hive.LogicalPlanToSQLSuite.beforeAll(LogicalPlanToSQLSuite.scala:23)
[info]   at org.scalatest.BeforeAndAfterAll$class.run(BeforeAndAfterAll.scala:253)
[info]   at org.apache.spark.sql.hive.LogicalPlanToSQLSuite.run(LogicalPlanToSQLSuite.scala:23)
[info]   at org.scalatest.tools.Framework.org$scalatest$tools$Framework$$runSuite(Framework.scala:462)
[info]   at org.scalatest.tools.Framework$ScalaTestTask.execute(Framework.scala:671)
[info]   at sbt.ForkMain$Run$2.call(ForkMain.java:296)
[info]   at sbt.ForkMain$Run$2.call(ForkMain.java:286)
[info]   at java.util.concurrent.FutureTask.run(FutureTask.java:266)
[info]   at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1142)
[info]   at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:617)
[info]   at java.lang.Thread.run(Thread.java:745)
```

/cc liancheng

Author: wangfei <wangfei_hello@126.com>

Closes #10682 from scwf/fix-test.

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

@@ -24,6 +24,9 @@ class LogicalPlanToSQLSuite extends SQLBuilderTest with SQLTestUtils {
   import testImplicits._
 
   protected override def beforeAll(): Unit = {
+    sql("DROP TABLE IF EXISTS t0")
+    sql("DROP TABLE IF EXISTS t1")
+    sql("DROP TABLE IF EXISTS t2")
     sqlContext.range(10).write.saveAsTable("t0")
 
     sqlContext