MTP: free leaked DIR after copyRecursive

Test: mmm -j
Test: atest mtp_ffs_handle_test
Change-Id: I572c8c0e982e89ed6f21f181e503b11e5439be59
diff --git a/media/mtp/MtpUtils.cpp b/media/mtp/MtpUtils.cpp
index 8564576..84a20d3 100644
--- a/media/mtp/MtpUtils.cpp
+++ b/media/mtp/MtpUtils.cpp
@@ -150,6 +150,7 @@
             ret += copyFile(oldFile.c_str(), newFile.c_str());
         }
     }
+    closedir(dir);
     return ret;
 }