add dir check before delete

sparkFilesDir is point to the current working dir in executor, and we only need to delete the tmp dir create by driver, for safe, we check it first.

core/src/main/scala/org/apache/spark/SparkEnv.scala

@@ -94,12 +94,20 @@ class SparkEnv (
 
     // Note that blockTransferService is stopped by BlockManager since it is started by it.
 
-    // If we only stop sc, but the driver process still run as a services then we need to delete 
-    // the tmp dir, if not, it will create too many tmp dirs
-    try {
-      Utils.deleteRecursively(new File(sparkFilesDir))
-    } catch {
-      case e: Exception => logError(s"Exception while deleting Spark temp dir: $sparkFilesDir", e)
+    /**
+     * If we only stop sc, but the driver process still run as a services then we need to delete
+     * the tmp dir, if not, it will create too many tmp dirs.
+     *
+     * We only need to delete the tmp dir create by driver, so we need to check the sparkFilesDir,
+     * because sparkFilesDir is point to the current working dir in executor.
+     */
+    if("." != sparkFilesDir){
+      try {
+        Utils.deleteRecursively(new File(sparkFilesDir))
+      } catch {
+        case e: Exception =>
+          logWarning(s"Exception while deleting Spark temp dir: $sparkFilesDir", e)
+      }
     }
   }