put 'curRequestSize = 0' after 'logDebug' it

This is a minor change. We should first logDebug($curRequestSize) and then set it to 0.

Author: Lijie Xu <csxulijie@gmail.com>

Closes #1477 from JerryLead/patch-1 and squashes the following commits:

aed722d [Lijie Xu] put 'curRequestSize = 0' after 'logDebug' it

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

@@ -180,9 +180,9 @@ object BlockFetcherIterator {
             if (curRequestSize >= targetRequestSize) {
               // Add this FetchRequest
               remoteRequests += new FetchRequest(address, curBlocks)
-              curRequestSize = 0
               curBlocks = new ArrayBuffer[(BlockId, Long)]
               logDebug(s"Creating fetch request of $curRequestSize at $address")
+              curRequestSize = 0
             }
           }
           // Add in the final request