[SPARK-6733][ Scheduler]Added scala.language.existentials

Author: Vinod K C <[email protected]>

Closes apache#5384 from vinodkc/Suppression_Scala_existential_code and squashes the following commits:

82a3a1f [Vinod K C] Added scala.language.existentials

Author: Vinod K C

core/src/main/scala/org/apache/spark/scheduler/DAGScheduler.scala

@@ -24,6 +24,7 @@ import java.util.concurrent.atomic.AtomicInteger
 
 import scala.collection.mutable.{ArrayBuffer, HashMap, HashSet, Map, Stack}
 import scala.concurrent.duration._
+import scala.language.existentials
 import scala.language.postfixOps
 import scala.util.control.NonFatal
 

mllib/src/test/scala/org/apache/spark/ml/recommendation/ALSSuite.scala

@@ -22,6 +22,7 @@ import java.util.Random
 
 import scala.collection.mutable
 import scala.collection.mutable.ArrayBuffer
+import scala.language.existentials
 
 import com.github.fommil.netlib.BLAS.{getInstance => blas}
 import org.scalatest.FunSuite