Revert "[SPARK-2468] Netty based block server / client module"

...ain/scala/org/apache/spark/network/netty/FileClient.scala

...he/spark/network/netty/FileClientChannelInitializer.scala

...la/org/apache/spark/network/netty/FileClientHandler.scala

...ain/scala/org/apache/spark/network/netty/FileHeader.scala

...ain/scala/org/apache/spark/network/netty/FileServer.scala

...he/spark/network/netty/FileServerChannelInitializer.scala

...la/org/apache/spark/network/netty/FileServerHandler.scala

.../scala/org/apache/spark/network/netty/ShuffleCopier.scala

.../scala/org/apache/spark/network/netty/ShuffleSender.scala

...ache/spark/network/netty/client/BlockFetchingClient.scala

...ark/network/netty/client/BlockFetchingClientFactory.scala

...e/spark/network/netty/client/ReferenceCountedBuffer.scala

...a/org/apache/spark/network/netty/server/BlockHeader.scala

...a/org/apache/spark/network/netty/server/BlockServer.scala

...pache/spark/network/netty/server/BlockServerHandler.scala

...scala/org/apache/spark/storage/BlockFetcherIterator.scala

...rc/main/scala/org/apache/spark/storage/BlockManager.scala

...ala/org/apache/spark/storage/BlockNotFoundException.scala

...ain/scala/org/apache/spark/storage/DiskBlockManager.scala

core/src/test/resources/netty-test-file.txt