[SPARK-5914] to run spark-submit requiring only user perm on windows

Because windows on-default does not grant read permission to jars except to admin, spark-submit would fail with "ClassNotFound" exception if user runs slave service with only user permission.
This fix is to add read permission to owner of the jar (which would be the slave service account in windows )

Author: Judy Nash <judynash@microsoft.com>

Closes #4742 from judynash/SPARK-5914 and squashes the following commits:

e288e56 [Judy Nash] Fix spacing and refactor code
1de3c0e [Judy Nash] [SPARK-5914] Enable spark-submit to run requiring only user permission on windows

core/src/main/scala/org/apache/spark/util/Utils.scala

@@ -440,6 +440,12 @@ private[spark] object Utils extends Logging {
     }
     // Make the file executable - That's necessary for scripts
     FileUtil.chmod(targetFile.getAbsolutePath, "a+x")
+
+    // Windows does not grant read permission by default to non-admin users
+    // Add read permission to owner explicitly
+    if (isWindows) {
+      FileUtil.chmod(targetFile.getAbsolutePath, "u+r")
+    }
   }
 
   /**