Fix S3A timeout issue and avoid memory leak.

Background: The open file triggered a timeout in the S3A connection pool.

Signed-off-by: Pascal Spörri <psp@zurich.ibm.com>

src/main/scala/org/apache/spark/shuffle/helper/S3ShuffleHelper.scala

@@ -118,6 +118,7 @@ object S3ShuffleHelper extends Logging {
  for (pos <- 0 until count) {
  result(pos) = input.readLong()
  }
+ input.close()
  result
  }
 }