[SPARK-6604][PySpark]Specify ip of python server scoket

In driver now will start a server socket and use a wildcard ip, use 127.0.0.0 is more reasonable, as we only use it by local Python process.
/cc davies

Author: linweizhong <linweizhong@huawei.com>

Closes #5256 from Sephiroth-Lin/SPARK-6604 and squashes the following commits:

7b3c633 [linweizhong] rephrase

core/src/main/scala/org/apache/spark/api/python/PythonRDD.scala

@@ -604,7 +604,7 @@ private[spark] object PythonRDD extends Logging {
    * The thread will terminate after all the data are sent or any exceptions happen.
    */
   private def serveIterator[T](items: Iterator[T], threadName: String): Int = {
-    val serverSocket = new ServerSocket(0, 1)
+    val serverSocket = new ServerSocket(0, 1, InetAddress.getByName("localhost"))
     // Close the socket if no connection in 3 seconds
     serverSocket.setSoTimeout(3000)