Increase Kryo buffer size in ALS since some arrays become big

mllib/src/main/scala/spark/mllib/recommendation/ALS.scala

@@ -418,6 +418,7 @@ object ALS {
     System.setProperty("spark.serializer", "spark.KryoSerializer")
     System.setProperty("spark.kryo.registrator", classOf[ALSRegistrator].getName)
     System.setProperty("spark.kryo.referenceTracking", "false")
+    System.setProperty("spark.kryoserializer.buffer.mb", "8")
     System.setProperty("spark.locality.wait", "10000")
     val sc = new SparkContext(master, "ALS")
     val ratings = sc.textFile(ratingsFile).map { line =>