Worker registration logging fix

Author: Andrew Ash <andrew@andrewash.com>

Closes apache#608 from ash211/patch-7 and squashes the following commits:

bd85f2a [Andrew Ash] Worker registration logging fix

(cherry picked from commit c0795cf)
Signed-off-by: Aaron Davidson <aaron@databricks.com>

core/src/main/scala/org/apache/spark/deploy/master/Master.scala

@@ -168,7 +168,7 @@ private[spark] class Master(host: String, port: Int, webUiPort: Int) extends Act
 
     case RegisterWorker(id, workerHost, workerPort, cores, memory, workerWebUiPort, publicAddress) => {
       logInfo("Registering worker %s:%d with %d cores, %s RAM".format(
-        host, workerPort, cores, Utils.megabytesToString(memory)))
+        workerHost, workerPort, cores, Utils.megabytesToString(memory)))
       if (state == RecoveryState.STANDBY) {
         // ignore, don't send response
       } else if (idToWorker.contains(id)) {