Change a parent class loader of ExecutorURLClassLoader.

Author: ueshin

core/src/main/scala/org/apache/spark/executor/Executor.scala

@@ -293,7 +293,7 @@ private[spark] class Executor(
    * created by the interpreter to the search path
    */
   private def createClassLoader(): ExecutorURLClassLoader = {
-    val loader = this.getClass.getClassLoader
+    val loader = Thread.currentThread().getContextClassLoader
 
     // For each of the jars in the jarSet, add them to the class loader.
     // We assume each of the files has already been fetched.