Revert "[SPARK-6028][Core]A new RPC implemetation based on the network module"

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

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

...rc/main/scala/org/apache/spark/deploy/worker/Worker.scala

.../scala/org/apache/spark/deploy/worker/WorkerWatcher.scala

.../src/main/scala/org/apache/spark/rpc/RpcCallContext.scala

core/src/main/scala/org/apache/spark/rpc/RpcEndpoint.scala

...a/org/apache/spark/rpc/RpcEndpointNotFoundException.scala

core/src/main/scala/org/apache/spark/rpc/RpcEnv.scala

...src/main/scala/org/apache/spark/rpc/akka/AkkaRpcEnv.scala

...rc/main/scala/org/apache/spark/rpc/netty/Dispatcher.scala

...rc/main/scala/org/apache/spark/rpc/netty/IDVerifier.scala

core/src/main/scala/org/apache/spark/rpc/netty/Inbox.scala

...in/scala/org/apache/spark/rpc/netty/NettyRpcAddress.scala

...cala/org/apache/spark/rpc/netty/NettyRpcCallContext.scala

...c/main/scala/org/apache/spark/rpc/netty/NettyRpcEnv.scala

.../org/apache/spark/storage/BlockManagerSlaveEndpoint.scala

core/src/main/scala/org/apache/spark/util/ThreadUtils.scala

...c/test/scala/org/apache/spark/MapOutputTrackerSuite.scala

core/src/test/scala/org/apache/spark/SSLSampleConfigs.scala

...a/org/apache/spark/deploy/worker/WorkerWatcherSuite.scala