[MINOR] [PYSPARK] Set PYTHONPATH to python/lib/pyspark.zip rather than python/pyspark

As PR #5580 we have created pyspark.zip on building and set PYTHONPATH to python/lib/pyspark.zip, so to keep consistence update this.

Author: linweizhong <linweizhong@huawei.com>

Closes #6047 from Sephiroth-Lin/pyspark_pythonpath and squashes the following commits:

8cc3d96 [linweizhong] Set PYTHONPATH to python/lib/pyspark.zip rather than python/pyspark as PR#5580 we have create pyspark.zip on build

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

@@ -31,7 +31,7 @@ private[spark] object PythonUtils {
   def sparkPythonPath: String = {
     val pythonPath = new ArrayBuffer[String]
     for (sparkHome <- sys.env.get("SPARK_HOME")) {
-      pythonPath += Seq(sparkHome, "python").mkString(File.separator)
+      pythonPath += Seq(sparkHome, "python", "lib", "pyspark.zip").mkString(File.separator)
       pythonPath += Seq(sparkHome, "python", "lib", "py4j-0.8.2.1-src.zip").mkString(File.separator)
     }
     pythonPath ++= SparkContext.jarOfObject(this)