[Minor][MLLIB] Fix a formatting bug in toString method in Node.scala

1. predict(predict.toString) has already output prefix “predict” thus
it’s
duplicate to print ", predict = " again
2. there are some extra spaces

Author: Alain

mllib/src/main/scala/org/apache/spark/mllib/tree/model/Node.scala

@@ -51,8 +51,8 @@ class Node (
     var stats: Option[InformationGainStats]) extends Serializable with Logging {
 
   override def toString: String = {
-    "id = " + id + ", isLeaf = " + isLeaf + ", predict = " + predict + ", " +
-      "impurity =  " + impurity + ", split = " + split + ", stats = " + stats
+    "id = " + id + ", isLeaf = " + isLeaf + ", " + predict + ", " +
+      "impurity = " + impurity + ", split = " + split + ", stats = " + stats
   }
 
   /**

mllib/src/main/scala/org/apache/spark/mllib/tree/model/Split.scala

@@ -39,7 +39,7 @@ case class Split(
     categories: List[Double]) {
 
   override def toString: String = {
-    "Feature = " + feature + ", threshold = " + threshold + ", featureType =  " + featureType +
+    "Feature = " + feature + ", threshold = " + threshold + ", featureType = " + featureType +
       ", categories = " + categories
   }
 }
@@ -68,4 +68,3 @@ private[tree] class DummyHighSplit(feature: Int, featureType: FeatureType)
  */
 private[tree] class DummyCategoricalSplit(feature: Int, featureType: FeatureType)
   extends Split(feature, Double.MaxValue, featureType, List())
-