SPARK-5425: Use SerializationUtils to save properties in ResetSystemP…

…roperties trait

core/src/test/scala/org/apache/spark/util/ResetSystemProperties.scala

@@ -19,6 +19,7 @@ package org.apache.spark.util
 
 import java.util.Properties
 
+import org.apache.commons.lang3.SerializationUtils
 import org.scalatest.{BeforeAndAfterEach, Suite}
 
 /**
@@ -42,7 +43,11 @@ private[spark] trait ResetSystemProperties extends BeforeAndAfterEach { this: Su
   var oldProperties: Properties = null
 
   override def beforeEach(): Unit = {
-    oldProperties = new Properties(System.getProperties)
+    // we need SerializationUtils.clone instead of `new Properties(System.getProperties()` because
+    // the later way of creating a copy does not copy the properties but it initializes a new
+    // Properties object with the given properties as defaults. They are not recognized at all
+    // by standard Scala wrapper over Java Properties then.
+    oldProperties = SerializationUtils.clone(System.getProperties)
     super.beforeEach()
   }