[SPARK-20333] HashPartitioner should be compatible with num of child RDD's partitions.

## What changes were proposed in this pull request?

Fix test
"don't submit stage until its dependencies map outputs are registered (SPARK-5259)" ,
"run trivial shuffle with out-of-band executor failure and retry",
"reduce tasks should be placed locally with map output"
in DAGSchedulerSuite.

Author: jinxing <jinxing6042@126.com>

Closes #17634 from jinxing64/SPARK-20333.

core/src/test/scala/org/apache/spark/scheduler/DAGSchedulerSuite.scala

@@ -1277,10 +1277,10 @@ class DAGSchedulerSuite extends SparkFunSuite with LocalSparkContext with Timeou
    */
   test("don't submit stage until its dependencies map outputs are registered (SPARK-5259)") {
     val firstRDD = new MyRDD(sc, 3, Nil)
-    val firstShuffleDep = new ShuffleDependency(firstRDD, new HashPartitioner(2))
+    val firstShuffleDep = new ShuffleDependency(firstRDD, new HashPartitioner(3))
     val firstShuffleId = firstShuffleDep.shuffleId
     val shuffleMapRdd = new MyRDD(sc, 3, List(firstShuffleDep))
-    val shuffleDep = new ShuffleDependency(shuffleMapRdd, new HashPartitioner(2))
+    val shuffleDep = new ShuffleDependency(shuffleMapRdd, new HashPartitioner(1))
     val reduceRdd = new MyRDD(sc, 1, List(shuffleDep))
     submit(reduceRdd, Array(0))
 
@@ -1583,7 +1583,7 @@ class DAGSchedulerSuite extends SparkFunSuite with LocalSparkContext with Timeou
    */
   test("run trivial shuffle with out-of-band executor failure and retry") {
     val shuffleMapRdd = new MyRDD(sc, 2, Nil)
-    val shuffleDep = new ShuffleDependency(shuffleMapRdd, new HashPartitioner(2))
+    val shuffleDep = new ShuffleDependency(shuffleMapRdd, new HashPartitioner(1))
     val shuffleId = shuffleDep.shuffleId
     val reduceRdd = new MyRDD(sc, 1, List(shuffleDep), tracker = mapOutputTracker)
     submit(reduceRdd, Array(0))
@@ -1791,7 +1791,7 @@ class DAGSchedulerSuite extends SparkFunSuite with LocalSparkContext with Timeou
   test("reduce tasks should be placed locally with map output") {
     // Create a shuffleMapRdd with 1 partition
     val shuffleMapRdd = new MyRDD(sc, 1, Nil)
-    val shuffleDep = new ShuffleDependency(shuffleMapRdd, new HashPartitioner(2))
+    val shuffleDep = new ShuffleDependency(shuffleMapRdd, new HashPartitioner(1))
     val shuffleId = shuffleDep.shuffleId
     val reduceRdd = new MyRDD(sc, 1, List(shuffleDep), tracker = mapOutputTracker)
     submit(reduceRdd, Array(0))