fix a brought-in mistake in StorageLevel

Author: RongGu

core/src/main/scala/org/apache/spark/storage/StorageLevel.scala

@@ -70,10 +70,10 @@ class StorageLevel private(
   def toInt: Int = {
     var ret = 0
     if (useDisk_) {
-      ret |= 4
+      ret |= 8
     }
     if (useMemory_) {
-      ret |= 2
+      ret |= 4
     }
     if (useTachyon_) {
       ret |= 2
@@ -91,8 +91,8 @@ class StorageLevel private(
 
   override def readExternal(in: ObjectInput) {
     val flags = in.readByte()
-    useDisk_ = (flags & 4) != 0
-    useMemory_ = (flags & 2) != 0
+    useDisk_ = (flags & 8) != 0
+    useMemory_ = (flags & 4) != 0
     useTachyon_ = (flags & 2) != 0
     deserialized_ = (flags & 1) != 0
     replication_ = in.readByte()

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

@@ -156,12 +156,12 @@ class BlockManagerSuite extends FunSuite with BeforeAndAfter with PrivateMethodT
     assert(master.getLocations("a1").size === 0, "master did not remove a1")
     assert(master.getLocations("a2").size === 0, "master did not remove a2")
   }
-
+  
   test("master + 2 managers interaction") {
     store = new BlockManager("exec1", actorSystem, master, serializer, 2000, conf, securityMgr)
     store2 = new BlockManager("exec2", actorSystem, master, new KryoSerializer(conf), 2000, conf,
       securityMgr)
-
+    
     val peers = master.getPeers(store.blockManagerId, 1)
     assert(peers.size === 1, "master did not return the other manager as a peer")
     assert(peers.head === store2.blockManagerId, "peer returned by master is not the other manager")