[SPARK-8715] ArrayOutOfBoundsException fixed for DataFrameStatSuite.crosstab

cc yhuai

Author: Burak Yavuz <brkyvz@gmail.com>

Closes #7100 from brkyvz/ct-flakiness-fix and squashes the following commits:

abc299a [Burak Yavuz] change 'to' to until
7e96d7c [Burak Yavuz] ArrayOutOfBoundsException fixed for DataFrameStatSuite.crosstab

(cherry picked from commit ecacb1e88a)
Signed-off-by: Yin Huai <yhuai@databricks.com>

sql/core/src/test/scala/org/apache/spark/sql/DataFrameStatSuite.scala

@@ -78,7 +78,7 @@ class DataFrameStatSuite extends SparkFunSuite  {
     val rows = crosstab.collect()
     rows.foreach { row =>
       val i = row.getString(0).toInt
-      for (col <- 1 to 9) {
+      for (col <- 1 until columnNames.length) {
         val j = columnNames(col).toInt
         assert(row.getLong(col) === expected.getOrElse((i, j), 0).toLong)
       }