Upgraded to Akka 2 and fixed test execution (which was still parallel

core/src/main/scala/spark/CacheTracker.scala

core/src/main/scala/spark/MapOutputTracker.scala

core/src/main/scala/spark/SparkContext.scala

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

core/src/main/scala/spark/SparkException.scala

...in/scala/spark/scheduler/mesos/CoarseMesosScheduler.scala

core/src/main/scala/spark/storage/BlockManager.scala

core/src/main/scala/spark/storage/BlockManagerMaster.scala

core/src/test/scala/spark/CacheTrackerSuite.scala

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

project/SparkBuild.scala