[SPARK-2500] Move the logInfo for registering BlockManager to...

[SPARK-2500] Move the logInfo for registering BlockManager to BlockManagerMasterActor.register method

PR for SPARK-2500

Move the logInfo call for BlockManager to BlockManagerMasterActor.register instead of BlockManagerInfo constructor.

Previously the loginfo call for registering the registering a BlockManager is happening in the BlockManagerInfo constructor. This kind of confusing because the code could call "new BlockManagerInfo" without actually registering a BlockManager and could confuse when reading the log files.

Author: Henry Saputra <henry.saputra@gmail.com>

Closes #1424 from hsaputra/move_registerblockmanager_log_to_registration_method and squashes the following commits:

3370b4a [Henry Saputra] Move the loginfo for BlockManager to BlockManagerMasterActor.register instead of BlockManagerInfo constructor.

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

@@ -336,6 +336,10 @@ class BlockManagerMasterActor(val isLocal: Boolean, conf: SparkConf, listenerBus
         case None =>
           blockManagerIdByExecutor(id.executorId) = id
       }
+
+      logInfo("Registering block manager %s with %s RAM".format(
+        id.hostPort, Utils.bytesToString(maxMemSize)))
+
       blockManagerInfo(id) =
         new BlockManagerInfo(id, System.currentTimeMillis(), maxMemSize, slaveActor)
     }
@@ -432,9 +436,6 @@ private[spark] class BlockManagerInfo(
   // Mapping from block id to its status.
   private val _blocks = new JHashMap[BlockId, BlockStatus]
 
-  logInfo("Registering block manager %s with %s RAM".format(
-    blockManagerId.hostPort, Utils.bytesToString(maxMem)))
-
   def getStatus(blockId: BlockId) = Option(_blocks.get(blockId))
 
   def updateLastSeenMs() {