[SPARK-4661][Core] Minor code and docs cleanup

Author: zsxwing <zsxwing@gmail.com>

Closes #3521 from zsxwing/SPARK-4661 and squashes the following commits:

03cbe3f [zsxwing] Minor code and docs cleanup

Author: zsxwing

core/src/main/scala/org/apache/spark/rdd/PipedRDD.scala

@@ -63,7 +63,7 @@ private[spark] class PipedRDD[T: ClassTag](
 
   /**
    * A FilenameFilter that accepts anything that isn't equal to the name passed in.
-   * @param name of file or directory to leave out
+   * @param filterName of file or directory to leave out
    */
   class NotEqualsFileNameFilter(filterName: String) extends FilenameFilter {
     def accept(dir: File, name: String): Boolean = {

core/src/test/scala/org/apache/spark/ShuffleSuite.scala

@@ -270,7 +270,6 @@ object ShuffleSuite {
 
   def mergeCombineException(x: Int, y: Int): Int = {
     throw new SparkException("Exception for map-side combine.")
-    x + y
   }
 
   class NonJavaSerializableClass(val value: Int) extends Comparable[NonJavaSerializableClass] {

sql/hive/src/main/scala/org/apache/spark/sql/hive/execution/HiveTableScan.scala

@@ -38,7 +38,7 @@ import org.apache.spark.sql.hive._
  * :: DeveloperApi ::
  * The Hive table scan operator.  Column and partition pruning are both handled.
  *
- * @param attributes Attributes to be fetched from the Hive table.
+ * @param requestedAttributes Attributes to be fetched from the Hive table.
  * @param relation The Hive table be be scanned.
  * @param partitionPruningPred An optional partition pruning predicate for partitioned table.
  */