Removed the need to sleep in tests due to waiting for Akka to shut down

bagel/src/test/scala/bagel/BagelSuite.scala

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

core/src/test/scala/spark/AccumulatorSuite.scala

core/src/test/scala/spark/BroadcastSuite.scala

core/src/test/scala/spark/DistributedSuite.scala

core/src/test/scala/spark/FailureSuite.scala

core/src/test/scala/spark/FileServerSuite.scala

core/src/test/scala/spark/FileSuite.scala

core/src/test/scala/spark/PartitioningSuite.scala

core/src/test/scala/spark/PipedRDDSuite.scala

core/src/test/scala/spark/RDDSuite.scala

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

core/src/test/scala/spark/SizeEstimatorSuite.scala

core/src/test/scala/spark/SortingSuite.scala

core/src/test/scala/spark/ThreadingSuite.scala

core/src/test/scala/spark/storage/BlockManagerSuite.scala

repl/src/test/scala/spark/repl/ReplSuite.scala