[HOTFIX] Replace FunSuite with SparkFunSuite.

This fixes a build break introduced by merging a6430028,
which fails the new style checks that ensure that we use SparkFunSuite instead
of FunSuite.

core/src/test/scala/org/apache/spark/shuffle/sort/BypassMergeSortShuffleWriterSuite.scala

@@ -29,7 +29,7 @@ import org.mockito.Matchers._
 import org.mockito.Mockito._
 import org.mockito.invocation.InvocationOnMock
 import org.mockito.stubbing.Answer
-import org.scalatest.{BeforeAndAfterEach, FunSuite}
+import org.scalatest.BeforeAndAfterEach
 
 import org.apache.spark._
 import org.apache.spark.executor.{TaskMetrics, ShuffleWriteMetrics}
@@ -37,7 +37,7 @@ import org.apache.spark.serializer.{SerializerInstance, Serializer, JavaSerializ
 import org.apache.spark.storage._
 import org.apache.spark.util.Utils
 
-class BypassMergeSortShuffleWriterSuite extends FunSuite with BeforeAndAfterEach {
+class BypassMergeSortShuffleWriterSuite extends SparkFunSuite with BeforeAndAfterEach {
 
   @Mock(answer = RETURNS_SMART_NULLS) private var blockManager: BlockManager = _
   @Mock(answer = RETURNS_SMART_NULLS) private var diskBlockManager: DiskBlockManager = _

core/src/test/scala/org/apache/spark/shuffle/sort/SortShuffleWriterSuite.scala

@@ -18,11 +18,10 @@
 package org.apache.spark.shuffle.sort
 
 import org.mockito.Mockito._
-import org.scalatest.FunSuite
 
-import org.apache.spark.{Aggregator, SparkConf}
+import org.apache.spark.{Aggregator, SparkConf, SparkFunSuite}
 
-class SortShuffleWriterSuite extends FunSuite {
+class SortShuffleWriterSuite extends SparkFunSuite {
 
   import SortShuffleWriter._
 

core/src/test/scala/org/apache/spark/util/collection/ExternalSorterSuite.scala

@@ -19,12 +19,8 @@ package org.apache.spark.util.collection
 
 import scala.collection.mutable.ArrayBuffer
 
-import org.scalatest.PrivateMethodTester
-
 import scala.util.Random
 
-import org.scalatest.FunSuite
-
 import org.apache.spark._
 import org.apache.spark.serializer.{JavaSerializer, KryoSerializer}