Remove compiler warning from TaskContext change.

Author: Reynold Xin <rxin@apache.org>

Closes #2602 from rxin/warning and squashes the following commits:

130186b [Reynold Xin] Remove compiler warning from TaskContext change.

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

@@ -956,9 +956,9 @@ class PairRDDFunctions[K, V](self: RDD[(K, V)])
     val writeShard = (context: TaskContext, iter: Iterator[(K,V)]) => {
       // Hadoop wants a 32-bit task attempt ID, so if ours is bigger than Int.MaxValue, roll it
       // around by taking a mod. We expect that no task will be attempted 2 billion times.
-      val attemptNumber = (context.attemptId % Int.MaxValue).toInt
+      val attemptNumber = (context.getAttemptId % Int.MaxValue).toInt
       /* "reduce task" <split #> <attempt # = spark task #> */
-      val attemptId = newTaskAttemptID(jobtrackerID, stageId, isMap = false, context.partitionId,
+      val attemptId = newTaskAttemptID(jobtrackerID, stageId, isMap = false, context.getPartitionId,
         attemptNumber)
       val hadoopContext = newTaskAttemptContext(wrappedConf.value, attemptId)
       val format = outfmt.newInstance
@@ -1027,9 +1027,9 @@ class PairRDDFunctions[K, V](self: RDD[(K, V)])
     val writeToFile = (context: TaskContext, iter: Iterator[(K, V)]) => {
       // Hadoop wants a 32-bit task attempt ID, so if ours is bigger than Int.MaxValue, roll it
       // around by taking a mod. We expect that no task will be attempted 2 billion times.
-      val attemptNumber = (context.attemptId % Int.MaxValue).toInt
+      val attemptNumber = (context.getAttemptId % Int.MaxValue).toInt
 
-      writer.setup(context.stageId, context.partitionId, attemptNumber)
+      writer.setup(context.getStageId, context.getPartitionId, attemptNumber)
       writer.open()
       try {
         var count = 0