Fix bug where checking-in more than once would cause an infinite loop in UsageStatsService

- Forgot to increment loop variable :S

Bug:18239732
Change-Id: Ie37a83584d7849108dbfd3bd4cbb595520d488b1
diff --git a/services/usage/java/com/android/server/usage/UsageStatsDatabase.java b/services/usage/java/com/android/server/usage/UsageStatsDatabase.java
index 11da380..098b3ef 100644
--- a/services/usage/java/com/android/server/usage/UsageStatsDatabase.java
+++ b/services/usage/java/com/android/server/usage/UsageStatsDatabase.java
@@ -119,6 +119,7 @@
                 if (!files.valueAt(start).getBaseFile().getName().endsWith("-c")) {
                     break;
                 }
+                start++;
             }
 
             if (start == fileCount - 1) {